UPSC Prelims 1998 · General Studies
Question 139: Basic Numeracy
One local and another express train were proceeding in the same direction on parallel tracks at 29 km/hour and 65 km/hour respectively. The driver of the former noticed that it took exactly 16 seconds for the faster train to pass by him. What is the length of the faster train?
AnswerThe answer is (c).
Both trains go the same way, so the relative speed is 65 - 29 = 36 km/h = 36 x 5/18 = 10 m/s. The faster train takes 16 seconds to pass the driver of the slower one, so its length is relative speed x time = 10 x 16 = 160 m.
Why each option is right or wrong
- (a) 60 m would take 6 seconds at 10 m/s.
- (b) 120 m would take 12 seconds at 10 m/s.
- (c) Right: 10 m/s x 16 s = 160 m.
- (d) 240 m would take 24 seconds at 10 m/s.
Explanation: written by UPSC Grade, not by UPSC.
Source: UPSC, Civil Services (Preliminary) Examination 1998, General Studies. UPSC's own paper isn't online; the words are from a published compilation. The paper on upsc.gov.in.