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Coding & Decoding aptitude questions

Letter shifts, substitutions and pattern codes.

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Formula sheetCoding & Decoding: the essentialsFormula sheetCoding & Decoding: the essentialsShow

  • Positions: A = 1 to Z = 26, with landmarks E 5, J 10, O 15, T 20, Y 25. The opposite of position n is 27 − n: A and Z, M and N.
  • Write the shift under each letter of the example before guessing. A constant shift (+1, +2, −1) is the commonest code; Z + 1 wraps to A.
  • If the shift is not constant, check whether it grows with position (+1, +2, +3) or alternates in sign.
  • If no shift fits, reverse the word and compare again: reversal plus a small shift is the usual two-step code.
  • Number codes are usually the sum of the letter positions, that sum plus a constant, the word's length, or a rule such as n(n + 1). Confirm the rule on every example.
  • Letter-to-digit tables: build the full mapping from the examples, check repeated letters for consistency, and make sure the answer has one symbol per letter.
  • Sentence codes: intersect the code words of two sentences, and intersect their meanings.
  • Swapped symbols: rewrite the whole expression first, then apply BODMAS — × and ÷ before + and −, left to right.
  • Decoding: apply the shift in reverse, then re-encode to check.
  • Positions in the alphabet: the kth letter to the left of the nth is at n − k; the kth from the right is the (27 − k)th.

Example: MAP → OCR is a shift of +2 on every letter, so SUN → UWP.

Questions42

1

If CAT is DBU

In a certain code, CAT is written as DBU. How is DOG written in that code?

letter shift

45s

Easy2

Shifted, then reversed

If BOOK is coded as LPPC, how is PEN coded?

reverse · letter shift

75s

Medium3

Words coded as numbers

If RED is coded as 27 and BLUE as 40, how is PINK coded? (A = 1, B = 2, …, Z = 26.)

letter values

60s

Medium4

A substitution language

In a certain language: 'pit na som' means 'bring me water' 'som lat tuk' means 'water is cold' Which word means 'water'?

substitution

75s

Medium5

Shift by position

If ACE is coded as BEH, how is BUS coded?

variable shift

75s

Hard6

If TEACHER is VGCEJGT

In a certain code TEACHER is written as VGCEJGT. How is CHILDREN written in that code?

letter shift

75s

Medium7

If MADRAS is NBESBT

If MADRAS is coded as NBESBT, how is BOMBAY coded?

letter shift

60s

Easy8

If FRIEND is HTKGPF

If FRIEND is coded as HTKGPF, how is CANDLE coded?

letter shift

60s

Easy9

If SISTER is RHRSDQ

In a certain code SISTER is written as RHRSDQ. How is UNCLE written?

letter shift

60s

Easy10

If DELHI is CDKGH

If DELHI is coded as CDKGH, how is MUMBAI coded?

letter shift

60s

Easy11

If MOUSE is PRXVH

If MOUSE is coded as PRXVH, how is SHIFT coded?

letter shift

60s

Easy12

If ROAD is URDG

If ROAD is written as URDG, how is SWAN written?

letter shift

45s

Easy13

If SAND is TBOE

If the code for SAND is TBOE, what is the code for BIRD?

letter shift

45s

Easy14

If DOG is FQI

If DOG is coded as FQI, how is CAT coded?

letter shift

45s

Easy15

A backward shift on a longer word

If TRIPPLE is written as SQHOOKD, how is DISPOSE written?

letter shift

75s

Medium16

If NOIDA is OPJEB

If NOIDA is coded as OPJEB, how is DELHI coded?

letter shift

45s

Easy17

A shift that grows with position

If HOUSE is coded as IQXWJ, how is TABLE coded?

variable shift

90s

Hard18

Reversed, then shifted

If COMPUTER is written as RFUVQNPC, how is MEDICINE written?

reverse · letter shift

150s

Hard19

Words coded by letter sums

If CAT = 24 and DOG = 26, what is the code for PIG? (A = 1, B = 2, …, Z = 26.)

letter values

75s

Medium20

A code based on length

If REASON is coded as 5 and BELIEVED as 7, what is the code for GOVERNMENT?

letter values

60s

Medium21

Letters standing for digits

In a code, ROSE is written as 6821, CHAIR as 73456 and PREACH as 961473. How is SEARCH written?

substitution

135s

Hard22

Another digit substitution

If PALE is coded as 2134 and EARTH as 41590, how is PEARL coded?

substitution

105s

Medium23

Repeated letters in a code

If RIPPLE is written as 613382 and LIFE as 8192, how is PILLER written?

substitution

120s

Hard24

Two words, one table

If PAINT is coded as 74128 and EXCEL as 93596, how is ACCEPT coded?

substitution

120s

Hard25

Codes from two short words

If LOSE is coded as 1357 and GAIN as 2468, how is SLAIN coded?

substitution

90s

Medium26

A substitution language: good boys play

In a certain language: 'nik ka pa' means 'you are good' 'ka la ma' means 'good boys play' 'pa ni ma' means 'you play cricket' Which word means 'play'?

substitution language

90s

Medium27

Which word means 'good'

In a certain language: 'nik ka pa' means 'you are good' 'ka la ma' means 'good boys play' Which word means 'good'?

substitution language

60s

Easy28

Swapped arithmetic symbols

If '+' means '÷', '÷' means '−', '−' means '×' and '×' means '+', what is the value of: 12 + 6 ÷ 3 − 2 × 8

symbols

90s

Medium29

Letters standing for operations

If P denotes ÷, Q denotes ×, R denotes + and S denotes −, what is the value of: 18 Q 12 P 4 R 5 S 6

symbols

90s

Medium30

Another symbol swap

If '×' means '+', '+' means '÷', '−' means '×' and '÷' means '−', what is the value of: 6 × 4 + 2 − 3 ÷ 5

symbols

105s

Hard31

A numeric code rule

If 5 = 30, 6 = 42 and 7 = 56, then 8 = ?

number code

75s

Medium32

A smaller numeric code

If 2 = 6, 3 = 12 and 4 = 20, then 5 = ?

number code

60s

Easy33

Letters with odd values

If A = 1, B = 3, C = 5 and so on, what is the code for I?

letter values

60s

Medium34

Adding letter positions

If A = 1, B = 2, C = 3 and so on, what is the value of CAB?

letter values

30s

Easy35

Letters in alphabetical order

If the letters of the word MASTER are arranged in alphabetical order, which letter is fourth?

ordering

45s

Easy36

A simple reversal

If WORLD is coded as DLROW, how is INDIA coded?

reverse

45s

Easy37

Opposite letters of the alphabet

If ACT is coded as ZXG, how is BAD coded? (Each letter is replaced by its opposite in the alphabet.)

opposite letters

90s

Medium38

First half forward, second half back

If BOARD is coded as CPBSE, how is CHAIR coded?

letter shift

45s

Easy39

Decoding back to a word

In a certain code PLANT is written as QMBOU. What does TFBU stand for?

letter shift · decoding

75s

Medium40

Decoding a +2 shift

In a code where LIGHT is written as NKIJV, what does HQQF stand for?

letter shift · decoding

75s

Medium41

Position within the alphabet

Which letter is the eighth to the left of the twentieth letter from the left of the alphabet?

alphabet position

60s

Medium42

Counting from the right

Which is the seventh letter from the right in the English alphabet?

alphabet position

45s

Easy

Showing 42 of 42

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Coding & Decoding Aptitude Questions with Solutions

42 Coding & Decoding questions with hints, worked solutions and time targets — 17 easy · 18 medium · 7 hard. Letter shifts, substitutions and pattern codes.

  • Section: Logical Reasoning
  • Questions: 42
  • By difficulty: 17 easy · 18 medium · 7 hard
  • Cost: Free, unlimited on every plan

Letter shifts, substitutions and pattern codes.

Coding & Decoding: the essentials

  • Positions: A = 1 to Z = 26, with landmarks E 5, J 10, O 15, T 20, Y 25. The opposite of position n is 27 − n: A and Z, M and N.
  • Write the shift under each letter of the example before guessing. A constant shift (+1, +2, −1) is the commonest code; Z + 1 wraps to A.
  • If the shift is not constant, check whether it grows with position (+1, +2, +3) or alternates in sign.
  • If no shift fits, reverse the word and compare again: reversal plus a small shift is the usual two-step code.
  • Number codes are usually the sum of the letter positions, that sum plus a constant, the word's length, or a rule such as n(n + 1). Confirm the rule on every example.
  • Letter-to-digit tables: build the full mapping from the examples, check repeated letters for consistency, and make sure the answer has one symbol per letter.
  • Sentence codes: intersect the code words of two sentences, and intersect their meanings.
  • Swapped symbols: rewrite the whole expression first, then apply BODMAS — × and ÷ before + and −, left to right.
  • Decoding: apply the shift in reverse, then re-encode to check.
  • Positions in the alphabet: the kth letter to the left of the nth is at n − k; the kth from the right is the (27 − k)th.

Example: MAP → OCR is a shift of +2 on every letter, so SUN → UWP.

Questions

  1. If CAT is DBU Easy
    In a certain code, CAT is written as DBU. How is DOG written in that code?
  2. Shifted, then reversed Medium
    If BOOK is coded as LPPC, how is PEN coded?
  3. Words coded as numbers Medium
    If RED is coded as 27 and BLUE as 40, how is PINK coded? (A = 1, B = 2, …, Z = 26.)
  4. A substitution language Medium
    In a certain language: 'pit na som' means 'bring me water' 'som lat tuk' means 'water is cold' Which word means 'water'?
  5. Shift by position Hard
    If ACE is coded as BEH, how is BUS coded?
  6. If TEACHER is VGCEJGT Medium
    In a certain code TEACHER is written as VGCEJGT. How is CHILDREN written in that code?
  7. If MADRAS is NBESBT Easy
    If MADRAS is coded as NBESBT, how is BOMBAY coded?
  8. If FRIEND is HTKGPF Easy
    If FRIEND is coded as HTKGPF, how is CANDLE coded?
  9. If SISTER is RHRSDQ Easy
    In a certain code SISTER is written as RHRSDQ. How is UNCLE written?
  10. If DELHI is CDKGH Easy
    If DELHI is coded as CDKGH, how is MUMBAI coded?
  11. If MOUSE is PRXVH Easy
    If MOUSE is coded as PRXVH, how is SHIFT coded?
  12. If ROAD is URDG Easy
    If ROAD is written as URDG, how is SWAN written?
  13. If SAND is TBOE Easy
    If the code for SAND is TBOE, what is the code for BIRD?
  14. If DOG is FQI Easy
    If DOG is coded as FQI, how is CAT coded?
  15. A backward shift on a longer word Medium
    If TRIPPLE is written as SQHOOKD, how is DISPOSE written?
  16. If NOIDA is OPJEB Easy
    If NOIDA is coded as OPJEB, how is DELHI coded?
  17. A shift that grows with position Hard
    If HOUSE is coded as IQXWJ, how is TABLE coded?
  18. Reversed, then shifted Hard
    If COMPUTER is written as RFUVQNPC, how is MEDICINE written?
  19. Words coded by letter sums Medium
    If CAT = 24 and DOG = 26, what is the code for PIG? (A = 1, B = 2, …, Z = 26.)
  20. A code based on length Medium
    If REASON is coded as 5 and BELIEVED as 7, what is the code for GOVERNMENT?
  21. Letters standing for digits Hard
    In a code, ROSE is written as 6821, CHAIR as 73456 and PREACH as 961473. How is SEARCH written?
  22. Another digit substitution Medium
    If PALE is coded as 2134 and EARTH as 41590, how is PEARL coded?
  23. Repeated letters in a code Hard
    If RIPPLE is written as 613382 and LIFE as 8192, how is PILLER written?
  24. Two words, one table Hard
    If PAINT is coded as 74128 and EXCEL as 93596, how is ACCEPT coded?
  25. Codes from two short words Medium
    If LOSE is coded as 1357 and GAIN as 2468, how is SLAIN coded?
  26. A substitution language: good boys play Medium
    In a certain language: 'nik ka pa' means 'you are good' 'ka la ma' means 'good boys play' 'pa ni ma' means 'you play cricket' Which word means 'play'?
  27. Which word means 'good' Easy
    In a certain language: 'nik ka pa' means 'you are good' 'ka la ma' means 'good boys play' Which word means 'good'?
  28. Swapped arithmetic symbols Medium
    If '+' means '÷', '÷' means '−', '−' means '×' and '×' means '+', what is the value of: 12 + 6 ÷ 3 − 2 × 8
  29. Letters standing for operations Medium
    If P denotes ÷, Q denotes ×, R denotes + and S denotes −, what is the value of: 18 Q 12 P 4 R 5 S 6
  30. Another symbol swap Hard
    If '×' means '+', '+' means '÷', '−' means '×' and '÷' means '−', what is the value of: 6 × 4 + 2 − 3 ÷ 5
  31. A numeric code rule Medium
    If 5 = 30, 6 = 42 and 7 = 56, then 8 = ?
  32. A smaller numeric code Easy
    If 2 = 6, 3 = 12 and 4 = 20, then 5 = ?
  33. Letters with odd values Medium
    If A = 1, B = 3, C = 5 and so on, what is the code for I?
  34. Adding letter positions Easy
    If A = 1, B = 2, C = 3 and so on, what is the value of CAB?
  35. Letters in alphabetical order Easy
    If the letters of the word MASTER are arranged in alphabetical order, which letter is fourth?
  36. A simple reversal Easy
    If WORLD is coded as DLROW, how is INDIA coded?
  37. Opposite letters of the alphabet Medium
    If ACT is coded as ZXG, how is BAD coded? (Each letter is replaced by its opposite in the alphabet.)
  38. First half forward, second half back Easy
    If BOARD is coded as CPBSE, how is CHAIR coded?
  39. Decoding back to a word Medium
    In a certain code PLANT is written as QMBOU. What does TFBU stand for?
  40. Decoding a +2 shift Medium
    In a code where LIGHT is written as NKIJV, what does HQQF stand for?
  41. Position within the alphabet Medium
    Which letter is the eighth to the left of the twentieth letter from the left of the alphabet?
  42. Counting from the right Easy
    Which is the seventh letter from the right in the English alphabet?

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