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Math Help - clock problem

  1. #1
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    clock problem

    A watch, which gains 5 seconds every 3 minutes, is set right at 6a.m. What is the true time in the afternoon of the same day when the watch indicates a quarter past 3?


    My answer is 2:59:15 seconds but the book answer is 3:00:00
    Kindly check if you get a chance, appreciate your help.
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  2. #2
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    Re: clock problem

    Your book's answer is correct. Since you did not show how you got your answer it is impossible to say what you might have done wrong.
    Last edited by HallsofIvy; July 15th 2013 at 08:04 AM.
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  3. #3
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    Re: clock problem

    Time elapsed 15:15:00 on clock minus start time of 6:00:00 = 9:15:00 or 9.25 hrs which equals 555minutes
    Clock runs fast 555/3 *5 = 925 seconds fast 15 min 25 sec
    Correct time 14:59:35
    What did I do wrong?
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  4. #4
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    Re: clock problem

    @HallsOf Ivy I did similiar to bjhopper

    the difference between 6 a.m to 3:15 pm is 9 hours and 15 minutes which is equal to 555 minutes.
    So we have 555/3 = 185 minutes, which is equal to 185 * 5= 925 seconds or 15 minutes and 25 seconds. So I get 2:59:35.
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  5. #5
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    Re: clock problem

    I'll defer a direct answer until HallsofIvy gets back, but have you considered that the extra rate of the fast clock is not necessarily going to have a chance to act on the full 5 seconds in those last three minutes?

    -Dan
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