Enigma 383: Stop watch
10 February 2017
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From New Scientist #1532, 30th October 1986 [link]
My watch is pretty accurate — when it’s working. It has a sweep second-hand that advances in jerks, one each second; if the watch stops, it stops with the second hand pointing directly to one of the 60 “second” (or “minute”) marks round the rim. At noon all three hands are (naturally) pointing directly to the zero-minute mark.
At noon yesterday my watch was certainly working, but when I checked it at 6:00 pm I found that it had stopped. The angles the three hands made with each other all differed from 120 degrees by less than 1 degree.
At what time had my watch stopped? (Hours : minutes : seconds).