### Brain Teasers

# Losing Time

Math
Math brain teasers require computations to solve.

I was recently given a new watch for my birthday. However, as usual with my presents, it was quite useless as it loses 6 minutes every hour. I set it using my friend's accurate watch at midnight and it now shows 10:39am. I know that the watch stopped 21 minutes ago so what is the correct time now?

### Answer

12:11pm; since the clock is losing 6 minutes every hour, for every real hour which has passed, the clock will only show 54 minutes. Since the clock shows 10:39am, we know that 639 clock minutes have passed. This therefore equals 710 real minutes and hence 11 hrs 50 mins. The clock stopped 21 minutes ago, therefore the time must now be 12:11pm.Hide Answer Show Answer

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## Comments

May 23, 2002

Well Done!

Nice puzzle. I got this one wrong

I went the wrong way with my 6 minutes, thinking that when the watch showed 10am it was actually 16. Therefore, showing 100 made it 110 and the 39 minutes was nearly 4 minutes out making it 11:43ish then add the 21 minutes to make it nearly 124.

I should have twigged I was wrong when it wasn't a nice neat answer with rounded numbers, as all math problems seem to be ;)

I went the wrong way with my 6 minutes, thinking that when the watch showed 10am it was actually 16. Therefore, showing 100 made it 110 and the 39 minutes was nearly 4 minutes out making it 11:43ish then add the 21 minutes to make it nearly 124.

I should have twigged I was wrong when it wasn't a nice neat answer with rounded numbers, as all math problems seem to be ;)

it loses 1/10 th of passing time. Therefore 10:39 is 9/10 ths. Dividing by 9 gives 1:11 to add to the 10:39 making 11:50. Just add 21 min. Voila!

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