UPSC Prelims 2026 · CSAT Paper 2 · Set DMathematicsQ 80 / 80

UPSC Prelims 2026 CSAT Paper 2 — Question 80

Question

The speed of a train T is 100 km per hour and the speed of a person P is 4 km per hour. T crosses P in 15 seconds, if P travels along the direction of motion of T. If P travels along the opposite direction of T, then in how much time does T cross P, in seconds, approximately?

(a)13.51
(b)13.65
(c)13.85
(d)14.05

UnlockIAS answer: (c)13.85

Solution

Same direction: relative speed 96 km/h = 26.67 m/s, so train length = 26.67 × 15 = 400 m. Opposite direction: relative speed 104 km/h = 28.89 m/s, so time = 400 / 28.89 ≈ 13.85 s.

UnlockIAS expert key, prepared 24 May 2026 and cross-verified by re-deriving the answer — this is our key, not the official UPSC provisional key (awaited).

Section

Mathematics

Topic Reference

Numeracy — Trains (relative speed)

Official UPSC key still awaited

UPSC has announced (PIB Release 2262441, 18 May 2026) that the provisional answer key for CSE Prelims 2026 will be released “soon after Exam”. Until then, use the CSAT score calculator for your qualifying-status estimate, and join the per-question discussion below.

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Official Notification

PIB Release 2262441

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