Coding–decoding for IBPS Clerk

A coding–decoding question shows a word and its code, and asks you to code a new word with the same hidden rule. Or it gives a few coded sentences and asks for the code of one word. You are never asked to invent a rule. You are asked to spot one that the examiner has already used.

Almost every question in this topic runs on one of six patterns. Once you know them, you stop staring at a code and start testing: is it a shift? a reversal? opposites? That checklist is what makes the topic fast.

The one table you must know

Everything in letter coding depends on knowing letter positions without counting on your fingers.

Two aids:

• E J O T Y sit at 5, 10, 15, 20 and 25. From any of these you can reach a nearby letter in one or two steps.
• Opposite letters add up to 27: A–Z, B–Y, C–X, D–W, E–V, F–U, G–T, H–S, I–R, J–Q, K–P, L–O, M–N.

Shifts wrap around the alphabet: Z + 1 is A, and Y + 3 is B.

The six patterns

A seventh type, sentence coding, works differently and has its own section below.

The method

1. Write the position numbers of the word above it and the code below it.
2. Subtract letter by letter. A constant difference means a fixed shift. A steady change means a growing shift.
3. If the differences are random, check reversal (same letters) and opposites (pairs adding to 27).
4. Apply the rule to the new word, then check one letter again before you mark the answer.

Worked examples

Example 1 (fixed shift). If GOLD is coded as JROG, how is SILVER coded?

1. G(7) to J(10), O(15) to R(18), L(12) to O(15), D(4) to G(7). Each letter moves +3.
2. S to V, I to L, L to O, V to Y, E to H, R to U.
3. VLOYHU.

Example 2 (growing shift). If CARD is coded as DCUH, how is BOOK coded?

1. C to D is +1, A to C is +2, R to U is +3, D to H is +4.
2. B + 1 = C, O + 2 = Q, O + 3 = R, K + 4 = O.
3. CQRO.

Example 3 (reverse, then shift). If MANGO is coded as PHOBN, how is APPLE coded?

1. MANGO reversed is OGNAM. Each letter of OGNAM +1 gives PHOBN. The rule holds.
2. APPLE reversed is ELPPA. Each letter +1 gives FMQQB.
3. FMQQB.

Example 4 (opposite letters). If BANK is coded as YZMP, how is LOAN coded?

1. B(2) and Y(25) add to 27, A and Z add to 27, and so on. Each letter becomes its opposite.
2. L becomes O, O becomes L, A becomes Z, N becomes M.
3. OLZM.

Example 5 (number code). If CAT is coded as 24 and BAT as 23, what is the code for RAT?

1. C + A + T = 3 + 1 + 20 = 24. B + A + T = 2 + 1 + 20 = 23. The code is the sum of positions.
2. R + A + T = 18 + 1 + 20 = 39.
3. 39.

Sentence coding

Here whole words are coded, and the codes appear in a jumbled order. You find a word's code by comparing sentences that share it.

Example 6. In a code language:

• "sun rises in east" is written as "la pa ta ma"
• "east is bright" is written as "ma ro ni"
• "sun is hot" is written as "pa ro sa"

Find the codes.

1. "east" is in sentences 1 and 2. The only code common to both is ma.
2. "sun" is in sentences 1 and 3. The common code is pa.
3. "is" is in sentences 2 and 3. The common code is ro.
4. Sentence 2 then leaves "bright" as ni, and sentence 3 leaves "hot" as sa.
5. "rises" and "in" are "la" and "ta", but nothing tells you which is which. If a question asks for the code of "rises", the answer is "cannot be determined" or "either la or ta", depending on the options.

Conditional codes (mains)

The mains sometimes changes the rule by letter type. For example: "Each vowel is replaced by the next letter and each consonant by the previous letter." Handle these by marking the vowels in the word first, then coding letter by letter. Practice question 8 is one of these.

Common mistakes

• Counting positions on your fingers instead of using E J O T Y. It is slow and it drifts by one.
• Forgetting to wrap around after Z.
• Checking the rule on only the first two letters. A growing shift looks like a fixed shift until the third letter.
• Picking a sentence-code answer when two words share the same pair of codes. Say "cannot be determined" when the data does not separate them.

Practice

Aim for six minutes.

1. If PEN is coded as QFO, how is INK coded?
2. If ROAD is coded as URDG, how is LANE coded?
3. If FISH is coded as GKVL, how is BIRD coded?
4. If TRAIN is coded as NIART, how is COACH coded?
5. If GIVE is coded as TREV, how is TAKE coded?
6. If BAD is coded as 7, what is the code for FACE?
7. In a code language, "bank gives loan" is "ta ki mo", "loan is easy" is "mo ra su" and "easy bank account" is "su ta ne". What is the code for "gives"?
8. If each vowel in a word is replaced by the next letter and each consonant by the previous letter, how is CLERK coded?

Answers:

1. JOL. Each letter +1.
2. ODQH. Each letter +3: L to O, A to D, N to Q, E to H.
3. CKUH. FISH to GKVL is +1, +2, +3, +4. So B + 1 = C, I + 2 = K, R + 3 = U, D + 4 = H.
4. HCAOC. The word is reversed.
5. GZPV. Opposite letters: G and T, I and R, V and E, E and V all add to 27. T becomes G, A becomes Z, K(11) becomes P(16), E becomes V.
6. 15. BAD is 2 + 1 + 4 = 7. FACE is 6 + 1 + 3 + 5 = 15.
7. ki. "bank" is common to sentences 1 and 3 (ta). "loan" is common to sentences 1 and 2 (mo). That leaves ki for "gives".
8. BKFQJ. C to B, L to K, E (vowel) to F, R to Q, K to J.

What to do next

• Write out the opposite-letter pairs from memory until you can do all 13 in under 30 seconds.
• Solve 15 coding questions a day for a week, mixing letter and sentence types.
• For every sentence-coding question, list which codes are fixed and which are still paired. It builds the habit you need for the mains.
• Move next to alphabet-based questions, which use the same position table, and alphanumeric series.