X travels 6 km on a bicycle with average speeds of 5 km per hour, 10 km per hour and 4 km per hour during the first 1 km, the next 2 km and the remaining 3 km, respectively. Y travels the same distances with average speeds of 4 km per hour, 10 km per hour and 5 km per hour, respectively. How many minutes early will Y complete the journey if both X and Y start at the same time?
- (a) 3
- (b) 4
- (c) 5
- (d) 6 ✓ UPSC's answer
Why the answer is (d)
• Calculate X's time for the first 1 km: 1 km / 5 km/h = 0.2 hours.
• Calculate X's time for the next 2 km: 2 km / 10 km/h = 0.2 hours.
• Calculate X's time for the remaining 3 km: 3 km / 4 km/h = 0.75 hours.
• Total time for X is 0.2 + 0.2 + 0.75 = 1.15 hours.
• Calculate Y's time for the first 1 km: 1 km / 4 km/h = 0.25 hours.
• Calculate Y's time for the next 2 km: 2 km / 10 km/h = 0.2 hours.
• Calculate Y's time for the remaining 3 km: 3 km / 5 km/h = 0.6 hours.
• Total time for Y is 0.25 + 0.2 + 0.6 = 1.05 hours.
• The difference in time is 1.15 - 1.05 = 0.1 hours.
• Convert 0.1 hours to minutes: 0.1 * 60 = 6 minutes.
Why the other options are wrong
- (a) 3
- 3 minutes is incorrect because the actual time difference is 6 minutes.
- (b) 4
- 4 minutes is incorrect because the actual time difference is 6 minutes.
- (c) 5
- 5 minutes is incorrect because the actual time difference is 6 minutes.
Asked in the CSAT Paper II of the UPSC Civil Services Preliminary Examination 2026, held on 24 May 2026. Question and answer key: Union Public Service Commission. Explanation: UPSC Answer Check.