Learn by Novus · Open practice pack v1

Coding and decoding: full practice bank: open practice pack

100 untimed questions across 10 authored sections.

This is untimed educational practice for one cognitive skill. It is not a clinical, diagnostic, employment, or professionally recognized assessment, and it does not produce an IQ score or credential.

Learner worksheet

Coding and decoding is the skill of spotting the rule that turns a word into a code, then applying it in reverse. One hundred items in ten themed sections, each one self-contained: every rule you need is stated in the question itself. Work untimed and write the alphabet out beside you at first; recognising the common rule families is what builds speed later.

Choose one answer for each item. For a delayed-recall item, read its study text, cover it, and then answer without looking back.

Letter positions and number codes

Warm up with the most common code of all: each letter stands for its place in the alphabet, so A is 1 and Z is 26.

1. coding-decoding-s01-q01

In a code, each letter is replaced by its position in the alphabet, so A is 1 and B is 2. What number stands for the letter G?

  1. 5
  2. 6
  3. 7
  4. 8

Answer:

2. coding-decoding-s01-q02

In a code where A is 1 and Z is 26, which letter is written as the number 12?

  1. K
  2. L
  3. M
  4. N

Answer:

3. coding-decoding-s01-q03

In a code, each letter is replaced by its alphabet position, so CAB is written 3-1-2. How is BAD written?

  1. 2-1-4
  2. 2-1-3
  3. 1-2-4
  4. 4-1-2

Answer:

4. coding-decoding-s01-q04

In a code, DOG is written 4-15-7 because each letter is replaced by its alphabet position. How is COW written?

  1. 3-15-22
  2. 3-14-23
  3. 3-15-23
  4. 3-15-24

Answer:

5. coding-decoding-s01-q05

In a code where each letter is replaced by its alphabet position, which word is written 19-21-14?

  1. SIN
  2. SUN
  3. RUN
  4. SON

Answer:

6. coding-decoding-s01-q06

In a code, letters are replaced by their alphabet positions, so M is written 13. Which letter is written 20?

  1. S
  2. T
  3. U
  4. V

Answer:

7. coding-decoding-s01-q07

In a code, a word is written as the total of its letters' alphabet positions. What number stands for the word CAB?

  1. 6
  2. 7
  3. 8
  4. 9

Answer:

8. coding-decoding-s01-q08

In a code, ACE is written 1-3-5 because each letter is replaced by its alphabet position. Which word is written 2-4-6?

  1. BCF
  2. BDG
  3. ACF
  4. BDF

Answer:

9. coding-decoding-s01-q09

In a code, letters are replaced by their alphabet positions. Which letter has a position number exactly double that of D?

  1. G
  2. H
  3. I
  4. J

Answer:

10. coding-decoding-s01-q10

In a code, TEN is written 20-5-14 because each letter is replaced by its alphabet position. Which word is written 20-5-1?

  1. ATE
  2. EAT
  3. NET
  4. TEA

Answer:

Shifting letters forward and back

Shift codes replace every letter with one a fixed number of places away. Watch what happens at the ends of the alphabet, where counting wraps around.

11. coding-decoding-s02-q01

In a code, every letter is replaced by the letter one place later in the alphabet. How is CAT written?

  1. DBU
  2. BZS
  3. CBU
  4. DAU

Answer:

12. coding-decoding-s02-q02

In a code, every letter is replaced by the letter one place later in the alphabet. How is DOG written?

  1. EOH
  2. EPG
  3. EPH
  4. CNF

Answer:

13. coding-decoding-s02-q03

In a code, every letter is replaced by the letter two places later in the alphabet. How is BAT written?

  1. DCV
  2. CBU
  3. DBV
  4. DCU

Answer:

14. coding-decoding-s02-q04

In a code, every letter is replaced by the letter one place earlier in the alphabet. How is SUN written?

  1. TVO
  2. RTM
  3. RUM
  4. RTN

Answer:

15. coding-decoding-s02-q05

In a code, every letter is replaced by the letter two places earlier in the alphabet. How is FOG written?

  1. EMF
  2. DMF
  3. DNE
  4. DME

Answer:

16. coding-decoding-s02-q06

In a code, PEN is written QFO. Using the same rule, how is CUP written?

  1. DVQ
  2. BTO
  3. DUQ
  4. DVP

Answer:

17. coding-decoding-s02-q07

In a code, TIME is written SHLD. Using the same rule, how is DAY written?

  1. EBZ
  2. CZX
  3. CAX
  4. DZX

Answer:

18. coding-decoding-s02-q08

In a code, every letter is replaced by the letter one place later in the alphabet, and the alphabet is treated as a loop so Z becomes A. How is ZOO written?

  1. YNN
  2. AOO
  3. APP
  4. APO

Answer:

19. coding-decoding-s02-q09

In a code, every letter is replaced by the letter three places later in the alphabet. How is CAB written?

  1. EDC
  2. FDE
  3. FCE
  4. GED

Answer:

20. coding-decoding-s02-q10

A word was coded by moving each of its letters four places later in the alphabet, producing GEX. What was the original word?

  1. BAT
  2. CAT
  3. COT
  4. CAP

Answer:

Reversal and mirror codes

Two related families here: reversing the order of letters, and mirroring the alphabet so A pairs with Z. Decide which one is at work before you answer.

21. coding-decoding-s03-q01

In a code, every word is written with its letters in reverse order. How is DESK written?

  1. SKED
  2. KSDE
  3. EDSK
  4. KSED

Answer:

22. coding-decoding-s03-q02

In a code, LEMON is written NOMEL because the letters are reversed. How is APPLE written?

  1. ELPPA
  2. ELPAP
  3. EPLPA
  4. APPEL

Answer:

23. coding-decoding-s03-q03

In a code, each word of a phrase is reversed but the words stay in their original order. How is OPEN DOOR written?

  1. ROOD NEPO
  2. NEPO DOOR
  3. NEPO ROOD
  4. NOPE ROOD

Answer:

24. coding-decoding-s03-q04

In a code, GO HOME is written EMOH OG because the whole phrase, words included, is written backwards. How is SIT DOWN written?

  1. TIS NWOD
  2. NWOD TIS
  3. TIS DOWN
  4. NWOD SIT

Answer:

25. coding-decoding-s03-q05

In a mirror code, A is written Z, B is written Y, and so on down the alphabet. How is the letter C written?

  1. V
  2. W
  3. X
  4. Y

Answer:

26. coding-decoding-s03-q06

In a mirror code where A is written Z and B is written Y, how is the word CAB written?

  1. XYZ
  2. ZXY
  3. YZX
  4. XZY

Answer:

27. coding-decoding-s03-q07

In a mirror code where A is written Z, B is written Y, and so on, how is the word ZOO written?

  1. AKK
  2. BLL
  3. ALL
  4. ALK

Answer:

28. coding-decoding-s03-q08

In a mirror code where A is written Z, B is written Y, and so on, which word is written TLLW?

  1. FOOD
  2. GOLD
  3. WOOD
  4. GOOD

Answer:

29. coding-decoding-s03-q09

In a code, STOP is written TSPO because the letters are swapped in pairs. How is CARD written?

  1. ACRD
  2. CADR
  3. ACDR
  4. DRAC

Answer:

30. coding-decoding-s03-q10

In a code, HORSE is written ESROH because the letters are reversed. Which word is written TFARC?

  1. FRACT
  2. CRAFT
  3. CARFT
  4. TRACE

Answer:

Rearranged-letter codes

These codes keep every letter but move it somewhere else. Work out exactly which positions travel where before applying the rule.

31. coding-decoding-s04-q01

In a code, DEAR is written EDRA because neighbouring letters are swapped in pairs. How is FISH written?

  1. IFSH
  2. FIHS
  3. HSIF
  4. IFHS

Answer:

32. coding-decoding-s04-q02

In a code, CHAIR is written RHAIC because the first and last letters change places. How is TABLE written?

  1. EABLT
  2. ELBAT
  3. EABTL
  4. TABEL

Answer:

33. coding-decoding-s04-q03

In a code, MONEY is written ONEYM because the first letter moves to the end. How is PAPER written?

  1. REPAP
  2. PAPRE
  3. APERP
  4. APEPR

Answer:

34. coding-decoding-s04-q04

In a code, GARDEN is written NGARDE because the last letter moves to the front. How is PENCIL written?

  1. ENCILP
  2. LICNEP
  3. PENCLI
  4. LPENCI

Answer:

35. coding-decoding-s04-q05

In a code, TIME is written METI because the last two letters move to the front. How is CARD written?

  1. DRAC
  2. RDCA
  3. RDAC
  4. ARCD

Answer:

36. coding-decoding-s04-q06

In a code, the letters of a four-letter word are rewritten in the order second, first, fourth, third. How is LAMP written?

  1. ALMP
  2. LAPM
  3. ALPM
  4. PMAL

Answer:

37. coding-decoding-s04-q07

In a code, BOOK is written OKBO because the first two letters move to the end. How is DESK written?

  1. KSED
  2. SKED
  3. EDKS
  4. SKDE

Answer:

38. coding-decoding-s04-q08

In a code, every word is rewritten with its letters in alphabetical order. How is CHAIR written?

  1. ACHRI
  2. ACHIR
  3. AICHR
  4. RIAHC

Answer:

39. coding-decoding-s04-q09

In a code, the middle letter of a five-letter word is moved to the front and the rest keep their order. How is BRAIN written?

  1. ABRNI
  2. ARBIN
  3. ABRIN
  4. NIARB

Answer:

40. coding-decoding-s04-q10

In a code, a six-letter word is written with its two halves swapped. How is GARDEN written?

  1. NEDRAG
  2. DENGAR
  3. DENRAG
  4. RAGNED

Answer:

Working out the rule from an example

Now the rule is not stated. Compare the example word with its code letter by letter, name the rule, then apply it.

41. coding-decoding-s05-q01

In a code, MOON is written NPPO. Using the same rule, how is STAR written?

  1. SUBS
  2. TUBS
  3. TUAS
  4. RSZQ

Answer:

42. coding-decoding-s05-q02

In a code, HAND is written IBOE. Using the same rule, which word is written CMPX?

  1. GLOW
  2. CLAW
  3. BLOW
  4. BLEW

Answer:

43. coding-decoding-s05-q03

In a code, FLOWER is written GMPXFS. Using the same rule, how is GARDEN written?

  1. HBSDFO
  2. FZQCDM
  3. HBRDFO
  4. HBSEFO

Answer:

44. coding-decoding-s05-q04

In a code, CAT is written 3-1-20. Using the same rule, how is TAP written?

  1. 20-1-15
  2. 20-1-16
  3. 19-1-16
  4. 16-1-20

Answer:

45. coding-decoding-s05-q05

In a code, BOX is written YLC. Using the same rule, how is CAP written?

  1. XAK
  2. ZXK
  3. XZK
  4. XZL

Answer:

46. coding-decoding-s05-q06

In a code, ONE is written 15-14-5 and TWO is written 20-23-15. Using the same rule, how is SIX written?

  1. 19-9-24
  2. 18-9-24
  3. 19-8-24
  4. 19-9-23

Answer:

47. coding-decoding-s05-q07

In a code, a word is written as a single number, and RED is written 27. Using the same rule, how is BED written?

  1. 11
  2. 12
  3. 13
  4. 14

Answer:

48. coding-decoding-s05-q08

In a code, SUN is written TWQ. Using the same rule, how is DAY written?

  1. EBA
  2. ECB
  3. ECA
  4. EDB

Answer:

49. coding-decoding-s05-q09

In a code, FOUR is written EMRN. Using the same rule, how is FIVE written?

  1. EGRA
  2. EHSA
  3. EGSB
  4. EGSA

Answer:

50. coding-decoding-s05-q10

In a code, LAMP is written 12-1-13-16. Using the same rule, which word is written 4-9-19-8?

  1. DASH
  2. DISH
  3. FISH
  4. DISK

Answer:

Coded language: matching words to meanings

Each item gives short phrases in an invented language. Find the code word that appears in more than one phrase, match it to the meaning those phrases share, and work outwards from there.

51. coding-decoding-s06-q01

In a code language, "tor mel" means "red apple" and "mel dik" means "apple pie". Which code word means "apple"?

  1. mel
  2. tor
  3. dik
  4. It cannot be worked out

Answer:

52. coding-decoding-s06-q02

In a code language, "ral fim" means "cold night" and "fim dop" means "night sky". What does "ral" mean?

  1. night
  2. sky
  3. cold
  4. dark

Answer:

53. coding-decoding-s06-q03

In a code language, "mo ta ku" means "sweet mango juice", "ta si" means "mango tree", and "ku ne" means "juice bar". Which code word means "sweet"?

  1. mo
  2. ta
  3. ku
  4. si

Answer:

54. coding-decoding-s06-q04

In a code language, "pen zol" means "green field", "zol fim" means "field mouse", and "fim rak" means "mouse trap". What is the code for "green trap"?

  1. pen zol
  2. zol rak
  3. pen rak
  4. rak fim

Answer:

55. coding-decoding-s06-q05

In a code language, "lo ka mi" means "fast blue train", "ka su" means "blue sea", and "mi te" means "train station". What does "lo" mean?

  1. blue
  2. train
  3. station
  4. fast

Answer:

56. coding-decoding-s06-q06

In a code language, "sun" is "ora", "rises" is "tam", and "early" is "vek". Keeping the same word order, how would "sun rises early" be written?

  1. ora vek tam
  2. tam ora vek
  3. ora tam vek
  4. vek tam ora

Answer:

57. coding-decoding-s06-q07

In a code language, "fa lo mi" means "birds fly south", "mi ru" means "south wind", and "lo pen" means "fly high". Which code word means "birds"?

  1. lo
  2. mi
  3. fa
  4. ru

Answer:

58. coding-decoding-s06-q08

In a code language, "tin ko sa" means "buy fresh bread", "sa lem" means "bread shop", and "ko dor" means "fresh fruit". Which code word means "buy"?

  1. tin
  2. ko
  3. sa
  4. lem

Answer:

59. coding-decoding-s06-q09

In a code language, "ze bo" means "night sky", "bo fa" means "sky blue", and "fa ze" means "blue night". Which code word means "sky"?

  1. ze
  2. bo
  3. fa
  4. It cannot be worked out

Answer:

60. coding-decoding-s06-q10

In a code language, "mek tor sil pa" means "we play games daily", "sil ken" means "games room", "pa nod" means "daily paper", and "tor lim" means "play area". Which code word means "we"?

  1. tor
  2. sil
  3. pa
  4. mek

Answer:

Number and symbol substitutions

Codes that mix letters, digits, and symbols. Convert carefully in one direction at a time, and note whether any arithmetic is applied after the lookup.

61. coding-decoding-s07-q01

In a code, each letter is replaced by a number one more than its alphabet position, so A is written 2. How is CAB written?

  1. 3-1-2
  2. 2-4-3
  3. 4-1-3
  4. 4-2-3

Answer:

62. coding-decoding-s07-q02

In a code, each letter is replaced by double its alphabet position. How is BAD written?

  1. 2-1-4
  2. 4-2-6
  3. 4-2-8
  4. 8-2-4

Answer:

63. coding-decoding-s07-q03

In a code, a word is written as the total of its letters' alphabet positions. What number stands for the word BAG?

  1. 8
  2. 9
  3. 10
  4. 11

Answer:

64. coding-decoding-s07-q04

In a code, the digits are replaced by letters as follows: 1 is P, 2 is Q, 3 is R, 4 is S, and 5 is T. How is the number 3514 written?

  1. RTPS
  2. RPTS
  3. RTSP
  4. PRTS

Answer:

65. coding-decoding-s07-q05

In a code, the digits are replaced by letters as follows: 1 is P, 2 is Q, 3 is R, 4 is S, and 5 is T. Which number is written TQPR?

  1. 5231
  2. 2513
  3. 5123
  4. 5213

Answer:

66. coding-decoding-s07-q06

In a code, each letter is replaced by its alphabet position multiplied by 2, with 1 then subtracted, so A is written 1 and B is written 3. How is DAD written?

  1. 7-1-7
  2. 8-2-8
  3. 7-2-7
  4. 4-1-4

Answer:

67. coding-decoding-s07-q07

In a code, the symbol # stands for A, * stands for E, and @ stands for I, while every other letter is written as usual. How is the word BEAD written?

  1. B#*D
  2. B*@D
  3. B*#D
  4. BE#D

Answer:

68. coding-decoding-s07-q08

In a code, each letter is replaced by the alphabet position of the letter that follows it, so A is written 2. How is CAT written?

  1. 3-1-20
  2. 2-0-19
  3. 4-2-20
  4. 4-2-21

Answer:

69. coding-decoding-s07-q09

In a code, a word is written as the total of its letters' alphabet positions, and SEA is written 25. Which of these words is also written 25?

  1. CAT
  2. TEA
  3. LID
  4. BED

Answer:

70. coding-decoding-s07-q10

In a code, each letter is replaced by the number of the position it holds counting backwards from Z, so Z is written 1 and Y is written 2. How is BAD written?

  1. 2-1-4
  2. 24-26-23
  3. 25-26-24
  4. 25-26-23

Answer:

Conditional coding rules

Here the rule applies only to certain letters or in certain conditions. Sort the letters into the cases first, then code each case correctly.

71. coding-decoding-s08-q01

In a code, every vowel is replaced by the next letter of the alphabet and every consonant is left unchanged. How is TABLE written?

  1. TBBLF
  2. TABLF
  3. TBBLE
  4. UBCMF

Answer:

72. coding-decoding-s08-q02

In a code, every vowel is replaced by the next letter of the alphabet and every consonant is left unchanged. How is MUSIC written?

  1. MVSIC
  2. MUSJC
  3. MVSJC
  4. NVTJD

Answer:

73. coding-decoding-s08-q03

In a code, every consonant is replaced by the letter before it in the alphabet and every vowel is left unchanged. How is FACE written?

  1. EABE
  2. EABD
  3. FBCD
  4. EACE

Answer:

74. coding-decoding-s08-q04

In a code, a word is reversed if it has an even number of letters and left unchanged if it has an odd number. How is the pair HAND and CAT written?

  1. DNAH, TAC
  2. HAND, TAC
  3. DNAH, CAT
  4. HAND, CAT

Answer:

75. coding-decoding-s08-q05

In a code, any letter that appears more than once in a word is replaced by a star wherever it appears, and all other letters stay as they are. How is LETTER written?

  1. L****R
  2. LE**ER
  3. L*TT*R
  4. LETTER

Answer:

76. coding-decoding-s08-q06

In a code, every vowel is replaced by its alphabet position number and every consonant is left unchanged. How is HEAD written?

  1. H5AD
  2. 851D
  3. H15D
  4. H51D

Answer:

77. coding-decoding-s08-q07

In a code, a word is written backwards and the letter S is then added at the end. How is DREAM written?

  1. MAERD
  2. MAERDS
  3. SMAERD
  4. DREAMS

Answer:

78. coding-decoding-s08-q08

In a code, letters in odd positions move one place forward in the alphabet and letters in even positions move one place back. How is CODE written?

  1. DPEF
  2. BPCF
  3. DNED
  4. DNEF

Answer:

79. coding-decoding-s08-q09

In a code, a word that starts with a vowel is reversed, while a word that starts with a consonant has only its first and last letters swapped. How are OPEN and DESK written?

  1. NEPO, KESD
  2. OPEN, KESD
  3. NEPO, DESK
  4. NEPO, KSED

Answer:

80. coding-decoding-s08-q10

In a code, every third letter of a word is dropped and the remaining letters keep their order. How is CALENDAR written?

  1. CALEDA
  2. CAENAR
  3. CAENDR
  4. CAELNR

Answer:

Two-step codes

Each code here applies two operations one after the other. Do them strictly in the order stated, and when decoding, undo them in the opposite order.

81. coding-decoding-s09-q01

In a code, a word is first written backwards and then every letter moves one place forward in the alphabet. How is CAT written?

  1. UBD
  2. DBU
  3. UAD
  4. TAC

Answer:

82. coding-decoding-s09-q02

In a code, every letter first moves one place back in the alphabet and the word is then written backwards. How is DOG written?

  1. CNF
  2. FNC
  3. EPH
  4. HPE

Answer:

83. coding-decoding-s09-q03

In a code, every letter is first replaced by its mirror letter, so A becomes Z and B becomes Y, and the word is then written backwards. How is CAB written?

  1. XZY
  2. BAC
  3. ZYX
  4. YZX

Answer:

84. coding-decoding-s09-q04

In a code, every letter first moves two places forward in the alphabet and the first and last letters of the result are then swapped. How is LAMP written?

  1. RCON
  2. NCOR
  3. ROCN
  4. PMAL

Answer:

85. coding-decoding-s09-q05

In a code, the vowels of a word first move one place forward in the alphabet and the whole word is then written backwards. How is RAIN written?

  1. RBJN
  2. NJBR
  3. NIAR
  4. NJBS

Answer:

86. coding-decoding-s09-q06

In a code, a word is first written backwards and each letter is then replaced by its alphabet position. How is BAD written?

  1. 2-1-4
  2. 4-2-1
  3. 1-4-2
  4. 4-1-2

Answer:

87. coding-decoding-s09-q07

In a code, every letter first moves three places forward in the alphabet and the result is then written backwards. How is BOX written?

  1. ERA
  2. XOB
  3. ARE
  4. AER

Answer:

88. coding-decoding-s09-q08

In a code, the first two letters of a four-letter word are first moved to the end and every letter then moves one place back in the alphabet. How is DESK written?

  1. RJCD
  2. SKDE
  3. CDRJ
  4. RJDC

Answer:

89. coding-decoding-s09-q09

In a code, every vowel is first replaced by its alphabet position number and the whole word is then written backwards. How is FACE written?

  1. F1C5
  2. 5C1F
  3. 5C1E
  4. ECAF

Answer:

90. coding-decoding-s09-q10

A word was coded by moving each letter two places forward in the alphabet and then writing the result backwards, producing RCO. What was the original word?

  1. PAM
  2. MAT
  3. CAP
  4. MAP

Answer:

Breaking codes and advanced patterns

The hardest section: keyword alphabets, grid references, and codes you must break from a single worked example before you can use them.

91. coding-decoding-s10-q01

A code alphabet is built by writing the keyword MUSIC first and then the unused letters in their normal order, giving M, U, S, I, C, A, B, D, E and so on. The plain letter A is coded as the first letter of this new alphabet, B as the second, and so on. How is BAD written?

  1. UMI
  2. MUI
  3. UMS
  4. IMU

Answer:

92. coding-decoding-s10-q02

A code alphabet is built by writing the keyword MUSIC first and then the unused letters in their normal order, giving M, U, S, I, C, A, B, D, E and so on, with the plain letter A coded as the first entry, B as the second, and so on. Which word is written SMU?

  1. ABC
  2. BAC
  3. CBA
  4. CAB

Answer:

93. coding-decoding-s10-q03

In a code, the letters are set out in a five-column grid, row by row: A B C D E, then F G H I J, then K L M N O, then P Q R S T, then U V W X Y, with Z left out. Each letter is written as its row number followed by its column number, so H is 23. How is CAB written?

  1. 11-12-13
  2. 13-11-12
  3. 31-11-21
  4. 13-12-11

Answer:

94. coding-decoding-s10-q04

In a code, the letters are set out in a five-column grid, row by row: A B C D E, then F G H I J, then K L M N O, then P Q R S T, then U V W X Y, with Z left out, and each letter is written as its row number followed by its column number. Which word is written 45-15-11-33?

  1. TEAM
  2. MEAT
  3. TAME
  4. MATE

Answer:

95. coding-decoding-s10-q05

A message was coded by moving every letter the same number of places forward in the alphabet, and ZEBRA became DIFVE. How many places was each letter moved?

  1. 2
  2. 3
  3. 4
  4. 5

Answer:

96. coding-decoding-s10-q06

A message was coded by moving every letter four places forward in the alphabet. Which word was coded as QSRXL?

  1. MONEY
  2. MOUTH
  3. MOTHS
  4. MONTH

Answer:

97. coding-decoding-s10-q07

In a code, each letter is replaced by the alphabet position of the letter two places after it, so A is written 3. Which word is written 5-3-22?

  1. EAT
  2. CAT
  3. CAR
  4. ACT

Answer:

98. coding-decoding-s10-q08

In a code, a word is written as a single number: the alphabet positions of its letters are added together and the total is then multiplied by the number of letters. What number stands for FIG?

  1. 66
  2. 69
  3. 72
  4. 75

Answer:

99. coding-decoding-s10-q09

In a code, LIME is written NKOG and PEAR is written RGCT. Using the same rule, how is FISH written?

  1. HKSJ
  2. HJUJ
  3. GJTI
  4. HKUJ

Answer:

100. coding-decoding-s10-q10

A word was coded by moving each letter three places back in the alphabet and then writing the result backwards, producing BZX. What was the original word?

  1. AXE
  2. ACE
  3. ICE
  4. EAT

Answer:

Authored hints

This cognitive practice source does not publish authored hints. Every item is listed as missing a hint, and no hint text is generated or inferred.

100 worksheet items do not have an authored hint.

This source contains no authored hints. No hint text was generated.

Answer key

ItemChoiceAnswer
coding-decoding-s01-q01C7
coding-decoding-s01-q02BL
coding-decoding-s01-q03A2-1-4
coding-decoding-s01-q04C3-15-23
coding-decoding-s01-q05BSUN
coding-decoding-s01-q06BT
coding-decoding-s01-q07A6
coding-decoding-s01-q08DBDF
coding-decoding-s01-q09BH
coding-decoding-s01-q10DTEA
coding-decoding-s02-q01ADBU
coding-decoding-s02-q02CEPH
coding-decoding-s02-q03ADCV
coding-decoding-s02-q04BRTM
coding-decoding-s02-q05DDME
coding-decoding-s02-q06ADVQ
coding-decoding-s02-q07BCZX
coding-decoding-s02-q08CAPP
coding-decoding-s02-q09BFDE
coding-decoding-s02-q10BCAT
coding-decoding-s03-q01DKSED
coding-decoding-s03-q02AELPPA
coding-decoding-s03-q03CNEPO ROOD
coding-decoding-s03-q04BNWOD TIS
coding-decoding-s03-q05CX
coding-decoding-s03-q06DXZY
coding-decoding-s03-q07CALL
coding-decoding-s03-q08DGOOD
coding-decoding-s03-q09CACDR
coding-decoding-s03-q10BCRAFT
coding-decoding-s04-q01DIFHS
coding-decoding-s04-q02AEABLT
coding-decoding-s04-q03CAPERP
coding-decoding-s04-q04DLPENCI
coding-decoding-s04-q05BRDCA
coding-decoding-s04-q06CALPM
coding-decoding-s04-q07DSKDE
coding-decoding-s04-q08BACHIR
coding-decoding-s04-q09CABRIN
coding-decoding-s04-q10BDENGAR
coding-decoding-s05-q01BTUBS
coding-decoding-s05-q02CBLOW
coding-decoding-s05-q03DHBSEFO
coding-decoding-s05-q04B20-1-16
coding-decoding-s05-q05CXZK
coding-decoding-s05-q06A19-9-24
coding-decoding-s05-q07A11
coding-decoding-s05-q08BECB
coding-decoding-s05-q09DEGSA
coding-decoding-s05-q10BDISH
coding-decoding-s06-q01Amel
coding-decoding-s06-q02Ccold
coding-decoding-s06-q03Amo
coding-decoding-s06-q04Cpen rak
coding-decoding-s06-q05Dfast
coding-decoding-s06-q06Cora tam vek
coding-decoding-s06-q07Cfa
coding-decoding-s06-q08Atin
coding-decoding-s06-q09Bbo
coding-decoding-s06-q10Dmek
coding-decoding-s07-q01D4-2-3
coding-decoding-s07-q02C4-2-8
coding-decoding-s07-q03C10
coding-decoding-s07-q04ARTPS
coding-decoding-s07-q05D5213
coding-decoding-s07-q06A7-1-7
coding-decoding-s07-q07CB*#D
coding-decoding-s07-q08D4-2-21
coding-decoding-s07-q09CLID
coding-decoding-s07-q10D25-26-23
coding-decoding-s08-q01ATBBLF
coding-decoding-s08-q02CMVSJC
coding-decoding-s08-q03AEABE
coding-decoding-s08-q04CDNAH, CAT
coding-decoding-s08-q05AL****R
coding-decoding-s08-q06DH51D
coding-decoding-s08-q07BMAERDS
coding-decoding-s08-q08CDNED
coding-decoding-s08-q09ANEPO, KESD
coding-decoding-s08-q10BCAENAR
coding-decoding-s09-q01AUBD
coding-decoding-s09-q02BFNC
coding-decoding-s09-q03DYZX
coding-decoding-s09-q04ARCON
coding-decoding-s09-q05BNJBR
coding-decoding-s09-q06D4-1-2
coding-decoding-s09-q07CARE
coding-decoding-s09-q08ARJCD
coding-decoding-s09-q09B5C1F
coding-decoding-s09-q10DMAP
coding-decoding-s10-q01AUMI
coding-decoding-s10-q02DCAB
coding-decoding-s10-q03B13-11-12
coding-decoding-s10-q04ATEAM
coding-decoding-s10-q05C4
coding-decoding-s10-q06DMONTH
coding-decoding-s10-q07BCAT
coding-decoding-s10-q08A66
coding-decoding-s10-q09DHKUJ
coding-decoding-s10-q10BACE

Worked explanations

coding-decoding-s01-q01

Count forward from the start of the alphabet: A, B, C, D, E, F, G. G is the seventh letter, so its code is 7.

coding-decoding-s01-q02

Decoding means counting places rather than letters. The twelfth letter of the alphabet is L, so 12 decodes to L.

coding-decoding-s01-q03

Take the letters in the order they appear and swap each for its position: B is 2, A is 1, and D is 4. Keeping the original order is what stops a code turning into an anagram.

coding-decoding-s01-q04

C is the third letter, O the fifteenth, and W the twenty-third. Letters near the end of the alphabet are the easiest to miscount, so check them against a nearby landmark such as T at 20.

coding-decoding-s01-q05

Convert each number back to a letter: 19 is S, 21 is U, and 14 is N. Decoding is simply the same lookup carried out in the opposite direction.

coding-decoding-s01-q06

Counting on from the landmark you were given is quicker than starting at A: 13 is M, so 14 is N, 15 is O, and stepping on to 20 lands on T.

coding-decoding-s01-q07

Convert first, then add: C is 3, A is 1, and B is 2, giving a total of 6. A summing code loses the order of the letters, so several different words can share one number.

coding-decoding-s01-q08

Decode each number separately: 2 is B, 4 is D, and 6 is F. Noticing that the numbers rise in twos also tells you the letters must skip one place each time.

coding-decoding-s01-q09

Turn the letter into a number, do the arithmetic, then turn it back: D is 4, double 4 is 8, and the eighth letter is H.

coding-decoding-s01-q10

Only the last number has changed, so only the last letter changes: 1 is A, giving TEA. Words made of the same letters in a different order produce the same numbers in a different order.

coding-decoding-s02-q01

Step each letter on by one: C becomes D, A becomes B, and T becomes U. Every letter must move: leaving one unchanged is the most common slip.

coding-decoding-s02-q02

Moving each letter forward once gives E from D, P from O, and H from G. Moving backwards instead would give the wrong direction entirely.

coding-decoding-s02-q03

Count two places on for each letter: B to C to D, A to B to C, and T to U to V. Say the skipped letter aloud so you do not stop a place short.

coding-decoding-s02-q04

Step each letter back by one: S becomes R, U becomes T, and N becomes M. Reading the alphabet backwards for a moment makes this far less error-prone.

coding-decoding-s02-q05

Counting back two places gives D from F, M from O, and E from G. Check each letter separately rather than assuming the pattern of the first one repeats.

coding-decoding-s02-q06

Compare the example letter by letter to find the rule: each letter has moved one place forward. Applying that same single step to CUP gives DVQ.

coding-decoding-s02-q07

The example shows every letter moving one place back. Stepping back from A wraps round to the end of the alphabet, so A becomes Z and the word becomes CZX.

coding-decoding-s02-q08

Z has no later letter, so the loop carries it round to A, while each O steps on to P. Treating the alphabet as a circle is what keeps a shift code working at both ends.

coding-decoding-s02-q09

Counting on three places gives F from C, D from A, and E from B. With larger shifts it helps to count on your fingers rather than eyeballing the jump.

coding-decoding-s02-q10

To decode a shift, run it the other way: move each coded letter four places back, giving C from G, A from E, and T from X.

coding-decoding-s03-q01

Read the word from its last letter to its first: K, S, E, D. Writing the word out and reading it right to left is more reliable than trying to flip it in your head.

coding-decoding-s03-q02

Reversing means the last letter comes first and the first letter comes last, giving E, L, P, P, A. Repeated letters are easy to lose, so count that the code has as many letters as the original.

coding-decoding-s03-q03

Treat each word as its own small puzzle and leave the word order alone: OPEN reversed is NEPO and DOOR reversed is ROOD.

coding-decoding-s03-q04

Here the reversal runs across the whole phrase, so the last word arrives first and each word is itself reversed. Comparing the example's first coded word with the phrase's last word is what reveals this.

coding-decoding-s03-q05

Pair the alphabet from both ends inwards: the third letter from the start matches the third letter from the end, which is X. A quick check is that the two positions always add up to 27.

coding-decoding-s03-q06

Mirror each letter in turn while keeping the order: C pairs with X, A with Z, and B with Y. The order of the letters is untouched, only their identities change.

coding-decoding-s03-q07

Z sits at the far end, so it mirrors to A, and O at position fifteen mirrors to the twelfth letter, L. Using the rule that paired positions total 27 saves counting the whole alphabet.

coding-decoding-s03-q08

A mirror code undoes itself, so apply the same pairing to the code: T pairs with G, L with O, and W with D. Codes that are their own reverse are quicker to break than shifts.

coding-decoding-s03-q09

Split the word into pairs and turn each pair around on the spot: CA becomes AC and RD becomes DR. This is a local swap, not a full reversal, so the pairs themselves stay in place.

coding-decoding-s03-q10

Reversing is its own undoing, so read the code backwards to recover the word: C, R, A, F, T. If the result is not a real word, you have probably mis-sequenced a middle letter.

coding-decoding-s04-q01

Both pairs must be swapped, not just the first: FI becomes IF and SH becomes HS. Checking the example's second pair is what confirms the rule applies throughout.

coding-decoding-s04-q02

Only the two outer letters move, so the middle of the word is copied across untouched: E arrives at the front and T goes to the end.

coding-decoding-s04-q03

Lift the first letter off, shuffle everything else one place left, then add the lifted letter at the back. The remaining letters keep their relative order.

coding-decoding-s04-q04

This is the mirror image of moving the first letter to the end: the final letter jumps to the front and everything else shifts one place right.

coding-decoding-s04-q05

The block of the last two letters travels as a unit and keeps its internal order, so RD arrives first, followed by CA. Reversing inside the block would be a different rule altogether.

coding-decoding-s04-q06

Number the letters first, then read them off in the order the rule gives: A, L, P, M. Writing the position numbers above the letters makes rules like this almost mechanical.

coding-decoding-s04-q07

Split the word in half and swap the halves without disturbing the letters inside them, so SK comes first and DE follows.

coding-decoding-s04-q08

Sort the letters from earliest to latest in the alphabet: A, C, H, I, R. This code throws away the original order, so many words can share a single code.

coding-decoding-s04-q09

In a five-letter word the middle letter is the third one, so it leaves its place and leads the code while the remaining four follow in their original sequence.

coding-decoding-s04-q10

Cut the word down the middle into two blocks of three and exchange them, keeping each block's letters in order: DEN then GAR. Swapping halves is not the same as reversing the whole word.

coding-decoding-s05-q01

Line the example up letter by letter: every letter has advanced one place. Applying a single forward step to each letter of the new word gives TUBS.

coding-decoding-s05-q02

The example shows a one-place forward shift, so decoding means stepping one place back: C becomes B, M becomes L, P becomes O, and X becomes W.

coding-decoding-s05-q03

Checking two or three letters of the example is enough to identify a one-place forward shift, and longer words simply repeat it. Verify the middle letters too, since that is where a mis-stepped letter usually hides.

coding-decoding-s05-q04

The example matches each letter to its alphabet position, so the same lookup gives 20 for T, 1 for A, and 16 for P.

coding-decoding-s05-q05

The example letters are not shifted by a fixed amount; each one is paired with the letter the same distance from the opposite end of the alphabet. Mirroring CAP the same way gives XZK.

coding-decoding-s05-q06

Both examples map each letter to its alphabet position, and the shared letter O confirms it by appearing as 15 in each. S is 19, I is 9, and X is 24.

coding-decoding-s05-q07

Test the obvious idea first: the positions 18, 5, and 4 add up to 27, matching the example. Adding 2, 5, and 4 for the new word gives 11.

coding-decoding-s05-q08

The shift is not constant: the first letter moves one place, the second two, and the third three. Applying the same growing shift means the last letter runs past the end of the alphabet and loops round to B.

coding-decoding-s05-q09

Each letter moves backwards by its own position number: one place, then two, then three, then four. The last step loops past the start of the alphabet and lands on A.

coding-decoding-s05-q10

The example is a plain alphabet-position code, so convert the numbers back: 4 is D, 9 is I, 19 is S, and 8 is H. Checking every number rules out the near-misses that differ by a single letter.

coding-decoding-s06-q01

One code word appears in both phrases and one meaning appears in both translations, so they must belong together. That single overlap is the foothold every coded-language puzzle rests on.

coding-decoding-s06-q02

The word shared by both phrases must mean the shared idea of night, which leaves only one meaning for the other word in the first phrase.

coding-decoding-s06-q03

Pin down the words you can: one appears again with mango and another with juice. The word left over in the first phrase must carry the only meaning still unclaimed.

coding-decoding-s06-q04

Chain the overlaps: the first two phrases share field and the last two share mouse, which leaves one word each for green and trap. Coding a new phrase is just looking those two up.

coding-decoding-s06-q05

Two of the three words in the long phrase reappear elsewhere and can be identified from those pairings, so the remaining word takes the remaining meaning by elimination.

coding-decoding-s06-q06

When the dictionary is handed to you, coding is a straight substitution word by word, with the order preserved exactly as the question states.

coding-decoding-s06-q07

Each of the two short phrases shares one word with the long phrase, fixing the meanings of south and fly. Only one word of the long phrase is left unaccounted for.

coding-decoding-s06-q08

Work through the overlaps in turn: one word recurs with bread and another with fresh, so the third word of the opening phrase must be the verb.

coding-decoding-s06-q09

Every word appears in exactly two phrases, so match each word to the meaning those same two phrases share. The word common to the two phrases that both mention sky is the one you want.

coding-decoding-s06-q10

Three of the four words in the long phrase are each pinned down by a short phrase, leaving exactly one word and one meaning unmatched. Elimination is usually faster here than trying to translate every phrase in full.

coding-decoding-s07-q01

Do the lookup first and the arithmetic second: the positions 3, 1, and 2 each gain one to become 4, 2, and 3.

coding-decoding-s07-q02

Convert each letter to its position, then double it: 2 becomes 4, 1 becomes 2, and 4 becomes 8. Doubling a number is not the same as stepping two letters on, so always convert before calculating.

coding-decoding-s07-q03

Convert each letter and add: 2 for B, 1 for A, and 7 for G make 10. Adding the letters as you convert them is safer than converting all three and then adding.

coding-decoding-s07-q04

Replace the digits one at a time from left to right so the order of the number is preserved: 3, 5, 1, and 4 become R, T, P, and S.

coding-decoding-s07-q05

Read the key backwards to decode: T stands for 5, Q for 2, P for 1, and R for 3, keeping the same left-to-right order.

coding-decoding-s07-q06

Apply the two steps in the order given: the position 4 doubles to 8 and then loses 1 to give 7, while the position 1 doubles to 2 and loses 1 to give 1. Repeated letters must produce repeated numbers, which is a quick way to sanity-check the answer.

coding-decoding-s07-q07

Only the listed vowels are swapped, and each keeps its own place in the word, so the second letter becomes a star and the third a hash. Consonants are copied across unchanged.

coding-decoding-s07-q08

Move one letter along before you look up the number: C leads to D at 4, A leads to B at 2, and T leads to U at 21. This is the same as adding one to each position, but stepping through the letter makes the wrap at the end of the alphabet obvious.

coding-decoding-s07-q09

Total each word in turn and compare: 12, 9, and 4 add up to 25, while the others come to 24, 26, and 11. Summing codes lose so much information that different words often collide.

coding-decoding-s07-q10

Counting backwards means subtracting the ordinary position from 27, so 2 becomes 25, 1 becomes 26, and 4 becomes 23. That subtraction is quicker than counting down from Z each time.

coding-decoding-s08-q01

Mark the vowels before you start, then step only those forward: the second letter becomes B and the last becomes F, while the consonants are copied straight across.

coding-decoding-s08-q02

Both vowels must be treated, not just the first: one steps on to V and the other to J. Missing a later vowel is the usual error in conditional codes.

coding-decoding-s08-q03

This time the vowels are the ones that stay still, so only the first and third letters move back a place, becoming E and B.

coding-decoding-s08-q04

Count the letters before deciding what to do: the four-letter word meets the condition and is reversed, while the three-letter word does not and is copied as it stands.

coding-decoding-s08-q05

Two letters occur twice in this word, and the rule blanks out every copy of them, leaving only the two letters that appear once. Check every position, since a repeat can sit at either end.

coding-decoding-s08-q06

Only the vowels change form, and each keeps its own place, so the second letter becomes 5 and the third becomes 1. The consonants must remain letters, which rules out coding the whole word numerically.

coding-decoding-s08-q07

Carry out the steps strictly in the order given: reverse the letters first, and only then attach the extra letter to the end of what you have written.

coding-decoding-s08-q08

Number the positions before coding, then alternate the direction of each step: forward, back, forward, back. Writing the numbers above the letters keeps the alternation from drifting.

coding-decoding-s08-q09

Test each word against the condition separately: the first begins with a vowel so the whole word turns round, and the second begins with a consonant so only its outer letters trade places.

coding-decoding-s08-q10

Number the eight letters and strike out the third and the sixth, then read what is left in order. Counting in threes across the whole word, rather than restarting after each deletion, is what keeps the positions right.

coding-decoding-s09-q01

Write down the intermediate result rather than trying to hold it in your head: reversing gives T, A, C, and stepping each on gives U, B, D.

coding-decoding-s09-q02

Shift first, which gives C, N, F, and only then reverse the order. Stopping after the first step is the commonest mistake with two-step codes.

coding-decoding-s09-q03

Mirroring the letters gives X, Z, Y, and reversing that order gives Y, Z, X. Doing the two steps the other way round would produce a different answer, so the stated order matters.

coding-decoding-s09-q04

Shifting each letter two places gives N, C, O, R, and the swap then exchanges the outer two letters of that result. Note that the swap acts on the shifted letters, not the original ones.

coding-decoding-s09-q05

Treat the vowels first, giving R, B, J, N, then reverse that whole string. The consonants never move in the alphabet, but they do change position.

coding-decoding-s09-q06

Reverse the letters to get D, A, B, then convert each to 4, 1, and 2. Converting before reversing would give the same three numbers in the wrong order.

coding-decoding-s09-q07

The shift gives E, R, and A, since the last letter runs off the end of the alphabet and loops round. Reversing that string produces the final code.

coding-decoding-s09-q08

Rearranging first gives S, K, D, E, and stepping each letter back then gives R, J, C, D. Keep the intermediate word visible so the second step is applied to the right order.

coding-decoding-s09-q09

Substituting the vowels gives F, 1, C, 5, and reversing that sequence puts the number from the end at the front. Numbers reverse along with letters because they occupy positions in the string.

coding-decoding-s09-q10

Undo the steps in the opposite order to the one used for coding: read the code backwards to get O, C, R, then move each letter two places back.

coding-decoding-s10-q01

Line the two alphabets up in a row before coding: the second, first, and fourth entries of the keyword alphabet are U, M, and I. Writing the first ten entries out is usually enough for a short word.

coding-decoding-s10-q02

Decoding means asking where each coded letter sits in the keyword alphabet: the third, first, and second entries correspond to the third, first, and second letters of the ordinary alphabet.

coding-decoding-s10-q03

Find each letter's row first and its column second, then write the pair in that order. All three letters sit in the top row, so only the second digit changes.

coding-decoding-s10-q04

Read each pair as a row then a column and look the letter up: the fifth entry of the fourth row, the fifth of the first, the first of the first, and the third of the third. Words made of the same letters produce the same pairs in a different order, so decode every pair before choosing.

coding-decoding-s10-q05

Measure the gap on a letter that does not wrap around, such as the second one, then confirm it on another. The first letter looping from the end of the alphabet back to the start fits the same gap.

coding-decoding-s10-q06

Once the size of a shift is known, decoding is mechanical: move every coded letter four places back. Decoding just the first two letters narrows the field, but check the rest before settling.

coding-decoding-s10-q07

Reverse the arithmetic before the lookup: take two off each number to get 3, 1, and 20, then convert those positions into letters.

coding-decoding-s10-q08

The positions 6, 9, and 7 total 22, and multiplying by the three letters gives 66. Forgetting the second step and answering 22 is the trap this rule is built around.

coding-decoding-s10-q09

Two examples are better than one: both show every letter advancing two places, which rules out a rule that treats vowels differently. Applying that steady two-place step to each letter gives the code.

coding-decoding-s10-q10

Undo the last step first by reading the code backwards to get X, Z, B, then move each letter three places forward, allowing the count to loop past the end of the alphabet.