Make vegetable pizza in damaged microwave puzzle


You have a microwave whose timer is damaged and you don’t have any other watch except two hourglasses, Hourglass A Measures an exact 7 minutes and Hourglass B Measures an exact 4 minutes.

Using these two hour glasses, you need to make vegetable pizza for exact nine minutes in microwave. How will you?

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    1. Set both the hourglasses running from initial position. (0 min.)
    2. 4th Minute: When the 4-min hourglass runs out, reset it (reverse). At this point, the 7-min hourglass will have 3 min. left.
    3. 7th Minute: After the 7-min.hourglass runs out, reset that one also. At this point, the 4-min hourglass will have 1 min. left.
    4. 8th Minute: By the time the 4-min hourglass runs out (total 8 min. lapsed), the 7-min. hourglass will have drained 1 min. (after reset)
    5. Now, reset the 7-min hourglass again. Since it had run 1 minute after previous reset, it will run for one minute, taking the total time to 9 min.

    Viji_Pinarayi Expert Answered on 6th January 2017.
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