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September 30, 2008

Clock Problem ?

Suppose a clock's seconds hand is exactly on a
second’s mark (one of the sixty) and exactly 22
second marks ahead of the hour hand. What is
the time?

1 comment:

Secret Squïrrel said...

Since it is exactly 22 sec behind the second hand, the hour hand must also be on a seconds (=minute) mark. This only happens at o'clock and every 12 min after that. (eg 1:00, 1:12, 1:24,...2:00, 2:12, etc)

At all of these times, the second hand is pointing directly at the 12. The hour hand is 22 marks behind which puts it 2 marks before the 8 (=3 after the 7).

Therefore the time is 7 + (3 x 12) = 7:36.