BPSC 70th CCE Prelims General Studies · Question 99 of 143

Correct — D, EOJDJEFM. Crack the rule on the worked example before you touch the answer word. COMPUTER is C-O-M-P-U-T-E-R and its code is R-F-U-V-Q-N-P-C. The first clue is that the code begins with R and ends with C, while the plain word begins with C and ends with R: the string has been reversed. The second clue is what happened to the letters in between. Write COMPUTER, leave the first letter C and the last letter R untouched, and advance each of the six interior letters by one place in the alphabet — O→P, M→N, P→Q, U→V, T→U, E→F. That gives C-P-N-Q-V-U-F-R. Now reverse the whole string: R-F-U-V-Q-N-P-C, which is the given code exactly, letter for letter. The rule is therefore: keep the first and last letters as they are, shift every interior letter one step forward, then reverse. Apply it to MEDICINE, which is M-E-D-I-C-I-N-E. Keep M and the final E; advance the six interior letters E→F, D→E, I→J, C→D, I→J, N→O. That gives M-F-E-J-D-J-O-E. Reverse it: E-O-J-D-J-E-F-M — EOJDJEFM, option (d). Because both steps were verified against the example before being applied, this is a derivation rather than a guess, and there is no ambiguity left to resolve.

• (a)MFBDPDQF — It still begins with M, so the reversal step has not been carried out at all — and the interior letters do not follow the +1 shift either. It is a pure decoy that resembles a coded string without obeying any rule the example supports.
• (b)MFEDJOFM — Also begins with M, the first letter of the plain word, which is the tell-tale sign of the commonest error on this question type: solving the substitution correctly and then forgetting that the example was reversed. Check the first and last letters of the given code against the plain word before anything else and this option disappears.
• (c)EOJDEJEM — The dangerous one. Its first four letters, EOJD, match the correct answer exactly, so a candidate who works the front of the word and then reads off the option in a hurry will take it. The last four differ — EJEM against the correct JEFM — because the shift has been misapplied to the middle letters. Always finish the string before matching.

Coding-decoding questions supply a worked example and ask you to reverse-engineer the transformation, so the marks sit in the diagnosis, not the arithmetic. There are only a handful of transformation families and almost every question is a combination of two of them: positional shift (each letter moves a fixed number of places, as in a Caesar cipher), reversal (of the whole word, of pairs, or of alphabet position so that A↔Z, B↔Y and every pair sums to 27), substitution by symbol or number, and position-dependent rules where odd and even places behave differently. The efficient method is to compare the plain word and the code letter by letter and write the gap under each pair. A constant gap means a shift; a gap that alternates in sign means a paired rule; a code whose first letter matches the plain word's last letter means a reversal is in play. Two mechanical aids save time: the EJOTY mnemonic fixes E=5, J=10, O=15, T=20, Y=25 so you can find any letter's position in a second, and remembering that a letter and its mirror image sum to 27 handles the whole reverse-alphabet family.

The single most useful observation on this question takes two seconds and comes before any letter-shifting: the code RFUVQNPC starts with R and ends with C, and COMPUTER starts with C and ends with R. That mismatch tells you the word was reversed, and it immediately kills options (a) and (b), both of which still open with M. You are then choosing between (c) and (d), which share their first four letters, so the decision is made entirely at the tail. Work the string all the way to the end and reverse it fully rather than eyeballing the start. The rule also has a symmetric feature worth noticing — the first and last letters are exempt from the shift, which is why C survives as C and R as R, and why in MEDICINE the M and the final E pass through unchanged. Both fixed letters end up at the opposite ends after reversal, which is what makes EOJDJEFM begin with E and end with M.

• The rule: leave the first and last letters unchanged, shift each interior letter +1 in the alphabet, then reverse the whole string
• Verification on the example: COMPUTER → C P N Q V U F R → reversed → RFUVQNPC, matching the given code exactly
• Applied to MEDICINE: M F E J D J O E → reversed → EOJDJEFM
• Diagnostic shortcut: if the code's first letter equals the plain word's last letter, a reversal is part of the rule
• EJOTY device for letter positions — E=5, J=10, O=15, T=20, Y=25; and a letter plus its mirror in the alphabet always sums to 27

• Solving the substitution and forgetting the reversal — the mistake behind both options that still begin with M
• Matching an option after checking only its first two or three letters, when two options share a common prefix
• Applying the shift to the first and last letters as well; here they are deliberately exempt, which is what the example proves

BPSC puts several coding items in Paper I every year and rotates the family — letters to letters in 2024, letters to numbers in the 69th, letters to symbols and shift-pairs in the 71st — so prepare the method rather than a specific cipher. UPSC keeps coding-decoding out of the General Studies paper entirely; it belongs to the qualifying CSAT paper, where it appears far less often than data interpretation and comprehension.

• practice — not a real PYQ

  In a certain code language, PENCIL is written as QFODJM. How will BASKET be written in the same code language ?

  • (a)CBTLFU
  • (b)ABSJDS
  • (c)TEKSAB
  • (d)CBTKFU

  Answer(a) CBTLFU — every letter simply moves one place forward (P→Q, E→F, N→O, C→D, I→J, L→M), so B→C, A→B, S→T, K→L, E→F, T→U.

• practice — not a real PYQ

  If in a code language the alphabet is reversed so that A is written as Z and B as Y, how will the word DOG be written ?

  • (a)WLT
  • (b)GOD
  • (c)CPF
  • (d)ELH

  Answer(a) WLT — a letter and its mirror sum to 27, so D (4) becomes the 23rd letter W, O (15) becomes the 12th letter L, and G (7) becomes the 20th letter T.