Multiple choice

A watch that gains 20 seconds in 12 minutes was set right at 10:00 A.M. In the afternoon of the same day, when the watch indicated quarter past 7 o'clock, the true time is

  1. 7 P.M.

  2. 6 P.M.

  3. 5 P.M.

  4. 4 P.M.

  5. 8 P.M.
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A Correct answer
Explanation

The watch gains 20 seconds every 12 minutes, which is 100 seconds per hour. From 10:00 A.M. to 7:15 P.M. is 9 hours and 15 minutes (9.25 hours). The total gain is 9.25 * 100 = 925 seconds, which is 15 minutes and 25 seconds. Subtracting this from 7:15 P.M. gives 6:59:35 P.M., which is closest to 7 P.M.

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