Measuring 9 minutes from 2-hour glasses Puzzle

December 2, 2022

Measuring 9 minutes from 2-hour glasses Puzzle

Using only a Four-minute hourglass and a seven-minute hourglass, How will you measure exactly nine minutes?
Restriction:- The process should not take longer than nine minutes.

Solution

We measure 7 Minute from One Hourglass.
We reverse it at 7th minute
And, 4+4=8 Minutes from Second Hourglass – 8 Minutes
8 (from 1) – 7 (From 2) = 1 Minute – 1 Minutes
TOTAL = 9 MINUTES

EXPLANATION 0 Minutes – Start both hourglasses at the same time.
4 Minutes – The four-minute glass runs out. Flip the four-minute glass.
7 Minutes – The seven-minute glass runs out. Flip the seven-minute glass.
8 Minutes – The four-minute glass runs out; the seven-minute glass has been running for one minute. Flip the seven-minute glass.
9 Minutes – The seven-minute glass runs out.

Detailed Solution

0 Minutes – Start both hourglass at the same time.

4 Minutes – The four minute glass runs out. Flip the four minute glass.

7 Minutes – The seven minute glass runs out. Flip the seven minute glass.

8 Minutes – The four-minute glass runs out; the seven-minute glass has been running for one minute. Flip the seven-minute glass.

0 Minutes – Start both hourglass at the same time.

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