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  1. #1
    4 Star Lounger
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    Hourglass Figure

    You have a 4 minute and a 7 minute hourglass. How do you measure 9 minutes?
    <font color=blue><font face="Script MT Bold"><big>Rob</big></font face=script></font color=blue>

  2. #2
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    Re: Hourglass Figure

    <span style="background-color: #FFFF00; color: #000000; font-weight: bold"><font color=yellow>Start both hourglasses at the same time. Each time one of them runs down, turn it around immediately.
    The 9 minute period starts when you turn around the 4 minute hourglass for the 3rd time (i.e. after 12 minutes) and ends when you turn around the 7 minute hourglass for the 3rd time (i.e. after 21 minutes)</font color=yellow></span hi>

  3. #3
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    Re: Hourglass Figure

    Oh oh!! I gotta try this one!! <span style="background-color: #FFFF00; color: #000000; font-weight: bold"><font color=yellow>I would start the 7 minute hour glass. When it is empty, don't restart it but immediately start the 4 minute glass and let it run until it is half empty! </font color=yellow></span hi> <img src=/S/grin.gif border=0 alt=grin width=15 height=15>


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  4. #4
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    Re: Hourglass Figure

    <span style="background-color: #FFFF00; color: #000000; font-weight: bold"><font color=yellow>Even if I had those "hour" (sounds like a misnomer to me) glasses, I would tend to use my trusty stopwatch. It gets much better precision and is more general.</font color=yellow></span hi>

    Steve

  5. #5
    4 Star Lounger
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    Re: Hourglass Figure

    That would work, but my solution takes 9 minutes from the first turn.
    <font color=blue><font face="Script MT Bold"><big>Rob</big></font face=script></font color=blue>

  6. #6
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    Re: Hourglass Figure

    Or until it's only half-full! <img src=/S/devil.gif border=0 alt=devil width=15 height=15>
    <font color=blue><font face="Script MT Bold"><big>Rob</big></font face=script></font color=blue>

  7. #7
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    Re: Hourglass Figure

    See the world in a grain of sand - and so many of them! <img src=/S/dizzy.gif border=0 alt=dizzy width=15 height=15>
    <font color=blue><font face="Script MT Bold"><big>Rob</big></font face=script></font color=blue>

  8. #8
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    Re: Hourglass Figure

    <span style="background-color: #FFFF00; color: #000000; font-weight: bold"><font color=yellow>Start 4 & 7 minute hourglasses together.
    When 4 minute hourglass drains turn it over (4 minutes elapsed)
    When 7 minute hourglass drains turn it over (7 minutes elapsed)
    When 4 minute hourglass drains for 2nd time turn over 7 minute hourglass (8 minutes elapsed)
    The 7 minute hourglass will drain again in a further minute, total time elapsed is 9 minutes.</font color=yellow></span hi>

  9. #9
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    Re: Hourglass Figure

    Fools seldom differ!
    <font color=blue><font face="Script MT Bold"><big>Rob</big></font face=script></font color=blue>

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