Hourglasses puzzle

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You have two hourglasses. One measured 7 minutes and the other 11 minutes.
How will you measure the 15 minutes using only these two hourglasses? Now here’s the twist you are only allowed to turn the hourglasses a total two times mean you can turn any of the glass two times or both the hourglasses one time each.

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    Start both the hourglasses. The 7 minutes will be finished first. Immediately turn it upside down.When the hourglass with 11 minutes is finished (after 11 minutes).the second glass will still have sand for 3 minutes turn it upside down immediately .So now the sand will fall for 15 more minutes.(11+7-3).

    pnikam Expert Answered on 22nd August 2015.
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