UPSC Prelims 1999 · General Studies
Question 134: Basic Numeracy
The average speed of a train in the onward journey is 25% more than that of the return journey. The train halts for one hour on reaching the destination. The total time taken for the complete to-and-fro journey is 17 hours covering a distance of 800 km. The speed of the train in the onward journey is
AnswerThe answer is (d).
Total time is 17 hours including a 1-hour halt, so travelling time is 16 hours for 800 km, i.e. 400 km each way. Let the return speed be v; the onward speed is 1.25v. Then 400/(1.25v) + 400/v = 16, so 320/v + 400/v = 16, 720/v = 16 and v = 45 km/h. Onward speed = 1.25 x 45 = 56.25 km/h.
Why each option is right or wrong
- (a) Wrong. 45 km/h is the return speed.
- (b) Wrong. 47.06 is 800/17, which ignores the halt and the speed difference.
- (c) Wrong. At 50 km/h onward and 40 return the trip would take 18 hours, not 16.
- (d) Right. Onward speed is 56.25 km/h.
Explanation: written by UPSC Grade, not by UPSC.
Source: UPSC, Civil Services (Preliminary) Examination 1999, General Studies. UPSC's own paper isn't online; the words are from a published compilation. The paper on upsc.gov.in.