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Common Answers

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Puzzle - Answer

You have the misfortune to own an unreliable clock. This one loses exactly 10 minutes every hour. It is now showing 5:00am and you know that is was correct at midnight, when you set it. The clock stopped 8 hours ago, what is the correct time now?

 [Ref: ZVNA] © Kevin Stone

Answer: 2:00pm.

The clock is losing 10 minutes every hour, so for every real hour that has passed, the clock will only show 50 minutes.

The clock now shows 5:00am, so we know that 300 clock minutes have passed. As every 50 clock minutes is actually a real hour: 300 ÷ 50 = 6 hours. So the clock stopped at 6:00am.

As the clock stopped 8 hours ago, the time now must be 2.00pm. QED.

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