### Brain Teasers

# Clocks

A clock has twelve hours in a rotation of the hour hand, sixty minutes in the rotation of the minute hand, and sixty seconds in a rotation of a second hand. Using the following things, starting at 0 hours and 0 seconds, how much time is passing in all these intervals?

5 rotations of the second hand

2/12 rotation of the hour hand

3/6 rotation of the minute hand

3/4 rotation of the minute hand

5 rotations of the second hand

2/12 rotation of the hour hand

3/6 rotation of the minute hand

3/4 rotation of the minute hand

### Answer

The answer is three hours and twenty minutes. Five rotations of the second hand is five minutes, because a full rotation of the second hand is a minute. 2/12 rotations of the hour hand is two hours. 3/6 rotations of the minute hand is 30 minutes because 3/6 is equal to 1/2. 3/4 rotations of the minute hand is 45 minutes.Hide Answer Show Answer

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## Comments

Interesting.

The numbers looked like fractions, and when calculated, the answer is 55 minutes and 35 seconds.

I think they are fractions. 1 rotation of the hour hand is 12 hours. 2/12 rotation of the hour hand is 2 hours. Did I miss something?

Charla, they were fractions.

Here2, I don't think you missed anything as long as you got the correct answer.

Here2, I don't think you missed anything as long as you got the correct answer.

Isn't "sweep" a better word for what happens than "rotation?" It is really only the centerpoint that rotates.

Nice one. Thanks for posting.

The answer is 2 hours. During the 2/12 sweep of the hour hand all of the other events simultaneously occur.

Oh you're right! Count on a twelve year old not to notice that.

Interesting quiz... thanks.

... I didn't know this was a quiz...

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