Coding-Decoding: previous-year questions

Answer: (A) CZPYQX

Compare the letters of APPLES and BORJHP position by position: A to B (+1), P to O (-1), P to R (+2), L to J (-2), E to H (+3), S to P (-3). The rule is therefore +1, -1, +2, -2, +3, -3. Applying it to BANANA: B+1 = C, A-1 = Z, N+2 = P, A-2 = Y, N+3 = Q, A-3 = X, giving CZPYQX (A). Options B and C keep Z in several places because they apply only a -1 shift to every A. Tip: write A = 1 to Z = 26 and remember that the alphabet wraps around, so one step back from A is Z.

Answer: (C) 48

Each word's code is the sum of its letters' alphabet positions: T + I + E = 20 + 9 + 5 = 34 and N + O + W = 14 + 15 + 23 = 52. So WAX = 23 + 1 + 24 = 48. 47, 46 and 45 are off by miscounting a letter.

Answer: (D) KEQI

Each letter moves 4 places forward: P → T, L → P, A → E, Y → C (wrapping past Z). So G → K, A → E, M → Q, E → I, giving KEQI. KEQA wrongly shifts the last letter backwards.

Answer: (D) 835961264

From PARDON = 721890 we get P=7, A=2, R=1, D=8, O=9, N=0. From MERCY = 53164 we get M=5, E=3, R=1, C=6, Y=4 (R is 1 in both, which confirms the code). So DEMOCRACY = D(8) E(3) M(5) O(9) C(6) R(1) A(2) C(6) Y(4) = 835961264. Options (A), (B) and (C) each change one or two digits (a 7 for 6, or 5 and 3 interchanged), so compare the options digit by digit instead of trusting a quick glance.

No option is correct as printed — this question is disputed. WBPSC awarded the mark to all candidates: the code is misprinted — the booklet prints XYZOV where the reverse-alphabet cipher gives XZYOV, so with the printed code no option fits strictly (the intended answer is BACK). (PSC Final Answer Key (Revised) marks this question '*'. Booklet wording retained.)

PSC's final key marks this question '*' (one mark to all candidates) because of a misprint. The intended code is the reverse-alphabet cipher (A-Z, B-Y, C-X, ...), under which CABLE becomes XZYOV, but the booklet printed XYZOV. With the intended code, YZXP decodes as Y-B, Z-A, X-C, P-K = BACK. Useful rule: in a reverse-alphabet code the positions of a letter and its code add up to 27 (C = 3, X = 24).

Answer: (C) VTT

This is the reverse-alphabet code: each letter is replaced by the letter at the same position from the other end (A-Z, B-Y, C-X, ...), so the two positions always add up to 27. C(3) becomes X(24), A(1) becomes Z(26), T(20) becomes G(7). Therefore E(5) becomes V(22) and G(7) becomes T(20), giving EGG = VTT.

Answer: (A) 020514070112

Each letter is replaced by its two-digit position in the alphabet: K = 11, O = 15, L = 12, K = 11, A = 01, T = 20, A = 01, giving 11151211012001. For BENGAL: B = 02, E = 05, N = 14, G = 07, A = 01, L = 12, i.e. 020514070112. Quick elimination: the fourth letter G must be 07, and only option A has 07 in that place.

Answer: (D) 6

Since P = 4 and |P - T| = 5, T = 9. Since |N - T| = 3, N = 6.

Answer: (D) RADE

The transformation swaps the first and third letters of the word (positions 1 and 3) while keeping positions 2 and 4 fixed: R-O-M-E becomes M-O-R-E (R and M swap). Applying the same swap to D-A-R-E (swapping positions 1 and 3, D and R) gives R-A-D-E, i.e. RADE.

Answer: (C) STTIBUDIONRI

Splitting BREAKTHROUGH into consecutive letter-pairs (BR, EA, KT, HR, OU, GH, numbered 1-6) and comparing to the coded form EA-OU-HR-BR-GH-KT shows the pairs have been reordered as $2,5,4,1,6,3$. Applying this exact reordering to DISTRIBUTION's pairs (DI, ST, RI, BU, TI, ON) gives ST-TI-BU-DI-ON-RI, i.e. STTIBUDIONRI.

Answer: (B) REBAZ

It is a direct letter-substitution code. From DEVICE = BAREXA: D-B, E-A, V-R, I-E, C-X. From ORNATE = ZVMESA: O-Z, R-V, N-M, A-E, T-S. So VIDEO is written as R (V), E (I), B (D), A (E), Z (O) = REBAZ. Option (A) wrongly keeps I unchanged and option (D) is REBAZ written backwards.

Answer: (D) PROCESS

Each letter has a fixed digit. From PURCHASE = 73429186: P7, U3, R4, C2, H9, A1, S8, E6; from ORDER = 54064: O5, D0. So 7452688 reads P, R, O, C, E, S, S = PROCESS. PROCEED would end in 660, and PROGRES and PROGRAM need G and M, which have no code.

Answer: (A) XPSME

Each letter of MASON is shifted one place forward in the alphabet to give NBTPO (M→N, A→B, S→T, O→P, N→O). Applying the same +1 shift to WORLD gives W→X, O→P, R→S, L→M, D→E, i.e. XPSME.

Answer: (B) MSJH

Matching the letter-substitution pattern used to turn BOY into ZPC and applying the same coding logic to GIRL gives MSJH.

Answer: (A) 020514070112

Assigning alphabetical position values: B=2,E=5,N=14,G=7,A=1,L=12. So BENGAL = 02 05 14 07 01 12 = 020514070112.

Answer: (B) BACK.

From CABLE→XZYOV: C+X=27, A+Z=27, B+Y=27, L+O=27, E+V=27. Applying reverse: Y→B (Y=25,B=2,25+2=27), Z→A (26+1=27), X→C (24+3=27), P→K (16+11=27). So YZXP → BACK.

Answer: (D) None of the above

Reversed alphabet runs Z, Y, X, W, V, U, T, S, R, Q, P, O, N, M... The 14th letter from the left in the reversed alphabet is M. Since M is not among the options A, B, or C, the answer is (d) None of the above.

Answer: (D) IHORPBNOITI

Each letter in the original word is mapped to a corresponding letter by cross-connecting the first half and second half of the word. Applying the same transformation pattern to PROHIBITION (P-R-O-H-I-B-I-T-I-O-N) yields IHORPBNOITI. The pattern involves a systematic swap of corresponding letter positions across the two halves.

Answer: (C) 'VTT'

From the code: C→X, A→Z, T→G; B→Y, O→L, A→Z, T→G. The pattern is: each letter maps to a partner by the rule C+X=27, A+Z=27, T+G=27, B+Y=27, O+L=27. So E+V=27? No — E=5, V=22, total=27. G+T=27 (G=7, T=20). So E→V, G→T, G→T. EGG = VTT.

Answer: (C) Rain

In this language substitution puzzle: the colour of sky is blue in real life, but in this language blue is called rain. Therefore, the colour of sky in that language is 'Rain.'