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Coding-Decoding

Reasoning Ability · Core Logical Tools

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Overview

Coding replaces letters or words by a rule — shift, reversal, position values or opposite letters — which you decode and reapply.

Key points

Shift coding: each letter moves by a fixed number (COLD → DPME is +1).
Reverse coding: the word is written backwards, sometimes with a shift.
Number coding: letters replaced by positions (CAT = 3 1 20) or by sums of positions.
Opposite-letter coding: A ↔ Z, B ↔ Y (position sum 27).
Mixed rules: different shifts for odd and even positions.

Explanation

If the code length differs, look for added or removed letters.
Number codes may use the sum of letter positions (CAT = 3 + 1 + 20 = 24).
Check whether the code is applied to the reversed word.
Verify the rule on every letter before applying it.

Step by step

Align word and code.
Find the rule.
Encode the new word and verify.

Examples

COLD → DPME (+1 each).
TEACH → VGCEJ (+2 each), so LEARN → NGCTP.
If CAT = 24 (sum of positions), then DOG = 4 + 15 + 7 = 26.

Traps and advanced points

Trap: Checking only the first two letters.
Trap: Missing that the word was reversed.
Trap: Using position differences instead of sums.

Quick revision

Write shifts above letters.
Check reversal.
Sum of positions for number codes.

Practice MCQs

In a code, CHMRW is written as HMRWB. How will ADGJM be written?
1. GJMPS
2. VYBEH
3. EHKNQ
4. FILOR
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Answer: (d) FILOR. Every letter is shifted +5.
In a code, FKPUZ is written as INSXC. How will HKNQT be written?
1. JMPSV
2. KNQTW
3. LORUX
4. EHKNQ
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Answer: (b) KNQTW. Every letter is shifted +3.
In a code, INSXC is written as KPUZE. How will ORUXA be written?
1. MPSVY
2. QTWZC
3. PSVYB
4. RUXAD
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Answer: (b) QTWZC. Every letter is shifted +2.
In a code, KPUZE is written as QVAFK. How will KNQTW be written?
1. PSVYB
2. EHKNQ
3. QTWZC
4. RUXAD
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Answer: (c) QTWZC. Every letter is shifted +6.
In a code, NSXCH is written as SXCHM. How will RUXAD be written?
1. XADGJ
2. WZCFI
3. VYBEH
4. MPSVY
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Answer: (b) WZCFI. Every letter is shifted +5.
In a code, VAFKP is written as BGLQV. How will BEHKN be written?
1. HKNQT
2. VYBEH
3. ILORU
4. GJMPS
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Answer: (a) HKNQT. Every letter is shifted +6.
If the coding rule reverses the letters, how is AFELSZ coded?
1. FELSZA
2. BGFMTA
3. AFELSZ
4. ZSLEFA
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Answer: (d) ZSLEFA. Read the word from right to left.
If the coding rule reverses the letters, how is AMNUBI coded?
1. AMNUBI
2. BNOVCJ
3. MNUBIA
4. IBUNMA
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Answer: (d) IBUNMA. Read the word from right to left.
In a code, RWBGL is written as TYDIN. How will JMPSV be written?
1. HKNQT
2. KNQTW
3. LORUX
4. MPSVY
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Answer: (c) LORUX. Every letter is shifted +2.
In a code, DINSX is written as JOTYD. How will LORUX be written?
1. QTWZC
2. FILOR
3. SVYBE
4. RUXAD
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Answer: (d) RUXAD. Every letter is shifted +6.
In a code, ZEJOT is written as EJOTY. How will TWZCF be written?
1. ZCFIL
2. ORUXA
3. YBEHK
4. XADGJ
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Answer: (c) YBEHK. Every letter is shifted +5.
In a code, HMRWB is written as KPUZE. How will DGJMP be written?
1. FILOR
2. ADGJM
3. HKNQT
4. GJMPS
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Answer: (d) GJMPS. Every letter is shifted +3.
If the coding rule reverses the letters, how is AHOVCJ coded?
1. BIPWDK
2. HOVCJA
3. AHOVCJ
4. JCVOHA
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Answer: (d) JCVOHA. Read the word from right to left.
If the coding rule reverses the letters, how is AYVCJQ coded?
1. BZWDKR
2. YVCJQA
3. QJCVYA
4. AYVCJQ
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Answer: (c) QJCVYA. Read the word from right to left.
In a code, QVAFK is written as WBGLQ. How will YBEHK be written?
1. FILOR
2. EHKNQ
3. SVYBE
4. DGJMP
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Answer: (b) EHKNQ. Every letter is shifted +6.