SPRING is written in a code as UNUFRC. How will the word MOBILE be mentioned in that code language?

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Correct — A, OMEFPA. Set the two words one above the other and replace every letter by its position in the alphabet, A = 1 up to Z = 26. SPRING is 19-16-18-9-14-7 and UNUFRC is 21-14-21-6-18-3. Subtract position by position and the code stops being letters and becomes arithmetic: S to U is +2, P to N is −2, R to U is +3, I to F is −3, N to R is +4, G to C is −4. The step therefore grows 2, 3, 4 while the direction alternates forward, backward, forward, backward — a progressive alternating shift, not the constant shift most candidates are drilled on. Apply exactly the same six operations, in the same order, to MOBILE, which is 13-15-2-9-12-5. M plus 2 is 15, which is O. O minus 2 is 13, which is M. B plus 3 is 5, which is E. I minus 3 is 6, which is F. L plus 4 is 16, which is P. E minus 4 is 1, which is A. The code word is O-M-E-F-P-A, option (a). Now decode it back, because a coding answer you have not reversed is an answer you have not verified: O minus 2 gives M, M plus 2 gives O, E minus 3 gives B, F plus 3 gives I, P minus 4 gives L, A plus 4 gives E — MOBILE, exactly. No wrap-around is needed anywhere here, because the smallest result is E minus 4, which lands on position 1 and stops precisely at A rather than running past the start of the alphabet.

Why the other options are wrong — (b) The dangerous one, and it is engineered to be. It opens with the same two letters as the answer, O and M, so a candidate who checks the rule on the first pair of letters only, concludes the shift is a constant plus-two/minus-two and stops testing has no way at all to tell it from option (a). Its last three letters give the design away: G, N and C are exactly what a constant plus-two/minus-two rule produces from I, L and E. A candidate reasoning that way actually derives OMDGNC, cannot find it among the options, and settles for the string that differs from it by a single letter instead of going back and re-deriving the rule. The third letter is the entire question — it must be E, because the step has grown to 3 by then, and this option prints P.  (c) This option leaves the first letter untouched, M in the plain word and M in the code, and that alone rules it out: all six letters of SPRING moved when it became UNUFRC, so no letter of MOBILE may stay where it is. Past the first letter the shifts it would require are +1, +15, +10, +9 and +7 — no constant step, no growth, no alternation. Its job on the page is to catch the candidate who never derives a rule at all and picks whichever string most resembles the original word.  (d) Turning MOBILE into SEGRFT would need shifts of +6, −10, +5, +9, −6 and +15: no constant step, no growing step, no alternation and no mirror. It is deliberate noise, put there so that the four options are not all near-misses of one another, and it is chosen only by candidates guessing on the look and rhythm of the letters. It also fails the cheapest structural check available — not one of its letters sits where any simple forward or backward shift of MOBILE would put it.

Concept: Every letter-shift coding question in Indian competitive exams belongs to one small family, and that family is best handled as arithmetic on positions rather than as manipulation of letters. Convert each letter to its ordinal, A = 1 through Z = 26, and a code turns into a sequence of signed differences. Those differences then follow one of a handful of patterns: a constant shift, which is the Caesar cipher that Suetonius records Julius Caesar using with a step of three; an alternating shift, forward then backward; a progressive shift, in which the size of the step grows along the word; a mirrored substitution, where each letter is replaced by its opposite in the alphabet; or a straight letter-to-number substitution. BPSC's SPRING to UNUFRC combines two of these at once — the direction alternates and the magnitude progresses — which is precisely why a candidate trained only on the constant shift finds it slippery. The one working habit that covers the whole family is to write the difference sequence out as numbers before you look at the options at all. Written as letters the pattern is invisible; written as +2, −2, +3, −3, +4, −4 it cannot be missed. A standing hazard applies to all of them: a shift running past Z wraps round to A and one running below A wraps back to Z, so the arithmetic is done modulo 26.

State PCS 2025 Q2 — Science & Technology PYQ with Answer

State PCS 2025 Q2 — Science & Technology PYQ with Answer