A train 200 metres long is moving at the rate of 40 kmph. In how many seconds will it cross a man standing near the railway line?

(a) 12
(b) 15
(c) 16
(d) 18 ✓ UPSC's answer

Why the answer is (d)

• Convert the train's speed from km/h to m/s by multiplying 40 by 5/18, which equals 100/9 m/s.

• The distance to be covered to cross a stationary man is equal to the length of the train, which is 200 metres.

• Calculate the time using the formula Time = Distance / Speed, resulting in 200 / (100/9).

• Simplify the expression to 200 * 9 / 100, which equals 18 seconds.

• Therefore, the train takes 18 seconds to cross the man, matching option (d).

Why the other options are wrong

(a) 12: 12 seconds is incorrect because it does not result from the correct division of 200 metres by 100/9 m/s.
(b) 15: 15 seconds is incorrect because it is not the mathematical result of the distance divided by the converted speed.
(c) 16: 16 seconds is incorrect because it does not match the calculated time of 18 seconds derived from the given parameters.

Asked in the CSAT Paper II of the UPSC Civil Services Preliminary Examination 2018, held on 3 June 2018. Question and answer key: Union Public Service Commission. Explanation: UPSC Answer Check.