A watch loses 2 minutes in every 24 hours while another watch gains 2 minutes in every 24 hours. At a particular instant, the two watches showed an identical time. Which of the following statements is correct if 24-hour clock is followed?
Answer & explanation
Answer: (d) None of the above statements is correct.
Each day the two watches drift 4 minutes further apart. On a 24-hour dial they show the same time again only when the gap is a full 24 hours (1440 minutes), which takes 360 days. None of 30, 90 or 120 days works.
- One watch loses 2 min and the other gains 2 min a day, so the gap between them grows by 4 min a day.
- On a 24-hour clock the two dials match again when the gap reaches 24 × 60 = 1440 min.
- Days needed = 1440 ÷ 4 = 360.
- Check: after 120 days the gap is only 480 min (8 hours), so options (a) to (c) all fail.
Remember · Two clocks agree again when their total gap equals one full dial: 720 minutes on a 12-hour clock, 1440 minutes on a 24-hour clock.
Question and answer: UPSC's official GS Paper II (2017, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 30 Sept 2026 (how we verify). ·