** Puzzle:** Given two hourglass of 4 minutes and 7 minutes, the task is to measure 9 minutes.

__Solution__:

**At 0 minutes:**Start both hourglasses at the same time.

**At 4 minutes:**4 minutes hourglass runs out and flip it. 7 minutes hourglass is left with 3 minutes.

**At 7 minutes:**4 minutes hourglass is left with 1 minute. 7 minutes hourglass runs out and flip it.

**At 8 minutes:**4 minutes hourglass runs out and 7 is filled with 6 minutes and 1 minute on the other side. Flip it as the sand is left with 1 minute.

**At 9 minutes:**7 minutes hourglass becomes empty from above side.

Hence we measured 9 minutes.

This article is contributed by **Vikash Kumar**. Please write comments if you find anything incorrect, or you want to share more information about the topic discussed above

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