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?
Answer & explanation
Answer: (d) 6
Add the time for each stretch. X takes 12 + 12 + 45 = 69 minutes; Y takes 15 + 12 + 36 = 63 minutes, so Y finishes 6 minutes earlier.
- X: 1/5 h = 12 min; 2/10 h = 12 min; 3/4 h = 45 min. Total 69 min.
- Y: 1/4 h = 15 min; 2/10 h = 12 min; 3/5 h = 36 min. Total 63 min.
- Y is earlier by 69 − 63 = 6 minutes.
Remember · Average speed over a journey is never the average of the speeds; add time = distance ÷ speed for each stretch.
Question and answer: UPSC's provisional GS Paper II (2026, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 30 Sept 2026 (how we verify). ·