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?
- A.The two watches show the identical time again on completion of 30 days.
- B.The two watches show the identical time again on completion of 90 days.
- C.The two watches show the identical time again on completion of 120 days.
- D.None of the above statements is correct.
▶ Answer & Explanation
Correct answer: D. None of the above statements is correct.
For the two watches to show the same time again, the difference in their timekeeping must amount to a full 12-hour cycle (720 minutes). One watch loses 2 minutes every 24 hours, and the other gains 2 minutes every 24 hours, resulting in a relative difference of 4 minutes every 24 hours. To accumulate a difference of 720 minutes, it would take 720 minutes / 4 minutes/day = 180 days. Since none of the options match 180 days, no option is correct.
Source: UPSC csat 2017