In a watch, the minute hand crosses the hour hand for the third time exactly after every 3 hr 18 min and 15 s of watch time. What is the time gained or lost by this watch in one day?
Explanation:
In a watch that is running correct, the minute hand should cross the hour hand once in every 65 + 511 min. So they should ideally cross three times once in 3×72011=206011 min = 196.36 min. But in the watch under consideration they meet after every 3 hr, 18 min and 15 s, i.e. (3 × 60 + 18 + 1560) = 7934 min = 198.25 min. In other words, our watch is actually losing time (as it is slower than the normal watch). Hence, when our watch elapsed 198.25 min, it actually should have elapsed 196.36 min. So in a day, when our watch will elapse (60 × 24) = 1440, it should actually elapse 1440×196.36198.25 = 1426. 27. Hence, the amount of time lost by our watch in one day = (1440 – 1426.27) = 13.73, i.e. 13 min and 50 s (approximately).
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