Measure 9 minutes from 2 hourglasses puzzle

Using only a Four-minute hourglass and a seven-minute hourglass,
How will you measure exactly nine minutes?

Restriction:- Without the process taking longer than nine minutes.

hourglass

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SherlockHolmes Expert Asked on 6th September 2015 in Interview Puzzles.
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  • 1 Answer(s)
    Best answer

    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 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.
    9 Minutes – The seven minute glass runs out.

     

    Detective Expert Answered on 6th September 2015.

    Exactly what i thought

    on 4th July 2016.
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