SSC CGL 2025 Tier-I · 21 September 2025, Shift 3 · General Intelligence and Reasoning · Question 23 of 100

We transcribed this text from the pictures on a candidate's response sheet for this shift; the answer is the key SSC colour-marked on that sheet. Solution last reviewed 11 September 2026.

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SSC does not publish CGL question papers or a public answer key. From 2025 the candidate response sheet prints every question and option as a picture, so the text here is transcribed from those pictures for this shift and checked against them independently; where the layout carries meaning, the picture is shown as well. Each answer is the key SSC colour-marked on that sheet. SSC released a tentative key for challenge and later its final one, both only to candidates behind a login, and the sheet does not say which of the two it carries. The solutions are written by UnlockIAS.

A train 120 meters long takes 6 seconds to cross a man. What is the speed of the train in km/h?

(a)36
(b)72
(c)60
(d)75

Answer

Why

Correct — B.
Rule: to pass a man, a train covers just its own length.

Distance = 120 m, time = 6 s
Speed = 120 ÷ 6 = 20 m/s
Convert: 20 × 18⁄5 = 72 km/h → option (b).

Why the others are wrong

(a)
36 — 36 km/h is 10 m/s, half the true speed. At 10 m/s the train would take 12 s, not 6, to pass the man.
(c)
60 — 60 km/h is about 16.7 m/s. At that speed 120 m takes 7.2 s, not 6.
(d)
75 — 75 km/h is about 20.8 m/s, a shade too fast: 120 m would take about 5.76 s, not 6.

Concept

A man by the track has no length worth counting, so the train has passed him once its whole length has gone by. Distance = train length.

Metres and seconds give m/s. To convert to km/h multiply by 18⁄5, because 1 m/s is 3600 m in an hour, which is 3.6 km/h.

The stem does not say the man is moving, so he is taken as standing still. If he walked, the speed relative to him would change and the working would need his speed too.

Key facts

Passing a man or a pole: distance = length of the train.
1 m/s = 18⁄5 km/h = 3.6 km/h.
Passing a platform or a bridge: distance = train length + platform length.

Study next

Train crossing a platform or bridge, where the lengths addTwo trains crossing each other in opposite or the same directionRelative speed when the man is walking

Common traps

Multiplying by 5⁄18 instead of 18⁄5 when going from m/s to km/h, which gives about 5.6.

17 Sep 2025, 16:00, Reasoning Q.17 sets the same case: a 180 m train passes a point in 12 s, so 15 m/s, keyed 54 km/h.

24 Sep 2024, 12:30, Quant Q.5 extends it to two goods trains running towards each other, where the lengths add (132 + 108 = 240 m) and so do the speeds.

Related PYQs

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