Coding Decoding Questions: Rules and Solved Examples
Most codes are built on letter positions, reversal or matching words across sentences.
Coding-decoding questions show you how one word is written in a secret code. You find the rule, then use it to code or decode another word.
The rule is usually built on letter positions in the alphabet, on reversing order, or on matching words with codes across sentences. Learn those three ideas and most questions become routine.
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Types of Coding-Decoding Questions
- Letter shift
- Each letter moves forward or backward by a fixed number. CAT becomes DBU when each letter moves one step forward.
- Reverse and shift
- The word is written backwards, and the letters may also be shifted.
- Opposite letters
- Each letter is replaced by its mirror letter from the other end of the alphabet: A with Z, B with Y, and so on.
- Letter to number
- A word gets a number, usually from its letter positions added or multiplied.
- Sentence coding (new pattern)
- Several short sentences are each given a set of code words. You compare sentences to find which code belongs to which word.
Alphabet Positions to Memorise
Knowing positions by heart saves counting time in every question.
E J O T Y
What it gives you
5, 10, 15, 20, 25
Why it works
Every fifth letter. Count from the nearest anchor instead of from A.
Opposite pairs add to 27
What it gives you
A and Z, M and N, H and S
Why it works
Position 1 pairs with 26, 2 with 25, and so on. So the opposite of a letter at position n is at 27 minus n.
M is 13, N is 14
What it gives you
The middle of the alphabet
Why it works
Letters A to M are the first half, N to Z the second.
| Anchor | What it gives you | Why it works |
|---|---|---|
| E J O T Y | 5, 10, 15, 20, 25 | Every fifth letter. Count from the nearest anchor instead of from A. |
| Opposite pairs add to 27 | A and Z, M and N, H and S | Position 1 pairs with 26, 2 with 25, and so on. So the opposite of a letter at position n is at 27 minus n. |
| M is 13, N is 14 | The middle of the alphabet | Letters A to M are the first half, N to Z the second. |
How to Crack Any Code
- 1
Write the positions
Put each letter's position number under both the word and its code.
- 2
Compare letter by letter
Find the difference for each pair. If every difference is the same, it is a simple shift.
- 3
If the differences differ, try reversing
Write the word backwards and compare again. Then check for opposite letters (positions adding to 27).
- 4
Test the rule on every letter
A rule that fits only the first two letters is not the rule. Check all of them before you apply it.
- 5
For sentence coding, compare pairs
Find a word common to two sentences. The code common to the same two sentences belongs to that word.
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Worked Practice Questions
Original questions written for this page. Try each before reading the solution.
- 1
Practice question 1: In a code, CAT is written as DBU. How is DOG written?
C (3) to D (4), A (1) to B (2), T (20) to U (21). Each letter moves one step forward. D becomes E, O becomes P, G becomes H. Answer: EPH.
- 2
Practice question 2: In a code, PLANT is written as UOBMQ. How is GRAPE written?
Reverse PLANT to get TNALP. Now compare TNALP with UOBMQ: each letter moves one step forward. So the rule is reverse, then +1. GRAPE reversed is EPARG. Move each letter forward: F, Q, B, S, H. Answer: FQBSH.
- 3
Practice question 3: In a code, BOX is written as YLC. How is HIT written?
B (2) and Y (25) add to 27. O (15) and L (12) add to 27. X (24) and C (3) add to 27. So each letter is replaced by its opposite. H (8) becomes S (19), I (9) becomes R (18), T (20) becomes G (7). Answer: SRG.
- 4
Practice question 4: If CAB = 6 and DEED = 18, what is FACE?
CAB: 3 + 1 + 2 = 6. Multiplying also gives 6, so test the second example. DEED: 4 + 5 + 5 + 4 = 18, while the product is 400. So the rule is the sum of positions. FACE: 6 + 1 + 3 + 5 = 15. Answer: 15.
- 5
Practice question 5: "rain is heavy" is coded "ko mi ta", "heavy snow falls" is coded "ta pu zo" and "snow is white" is coded "pu mi ra". What are the codes for "rain" and "white"?
Sentences 1 and 2 share "heavy" and the code "ta", so heavy = ta. Sentences 1 and 3 share "is" and the code "mi", so is = mi. That leaves rain = ko. Sentences 2 and 3 share "snow" and "pu", so snow = pu. In sentence 3, the only code left is "ra", so white = ra.
Common Traps
- check_circleStopping at the first letter. CAT to DBU looks like +1 from C alone, but you must confirm A and T follow the same rule.
- check_circleForgetting the wrap-around. In a +1 shift, Z goes back to A. In a +2 shift, Y goes to A.
- check_circleMissing a reversed word. If the differences look random, write the word backwards before trying anything harder.
- check_circleTaking order as meaning in sentence coding. The codes are usually not in the same order as the words, so only common words and common codes count.
- check_circleOne example, two rules. As in practice question 4, a single example can fit more than one rule. Use every example given.
How Bank and SSC Papers Test This
The IBPS PO syllabus lists coding-decoding under reasoning, as a "new pattern" topic. It falls in the Reasoning Ability section of prelims and the Reasoning section of mains, both online multiple choice tests.
SSC CGL Tier 1 tests reasoning in its General Intelligence & Reasoning section, also as multiple choice questions. Letter shift, opposite letter and letter to number codes are the same skills there.
Because the bank syllabus names the "new pattern", practise sentence coding as well as the simpler letter shifts. The comparing method in practice question 5 works for any number of sentences.
FAQs
What is the fastest way to solve coding decoding questions?expand_more
Memorise the anchor positions E, J, O, T and Y (5, 10, 15, 20, 25) and the rule that opposite letters add to 27. Then compare positions letter by letter.
What is new pattern coding decoding?expand_more
Usually sentence coding: several sentences each get a set of code words, and you match words to codes by comparing sentences that share a word.
How do I find the opposite letter quickly?expand_more
Subtract the letter's position from 27. H is 8, so its opposite is at 19, which is S.
Is coding decoding asked in IBPS PO?expand_more
Yes. Coding-decoding is part of the IBPS PO reasoning syllabus for prelims and mains.
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