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~Z.
Lv 4
~Z. asked in Science & MathematicsMathematics · 2 decades ago

A light flashes every 2 min, a 2nd light flashes every 2.5 min, & a 3rd light flashes every 3 min. If all 3...

...flash together and 9 a.m., what is the next time they will flash together?

no spam please. ^_^;

4 Answers

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  • vb_4_net
    2 decades ago
    Favorite Answer

    First 9:02,9:04,9:08,...,9:30

    Second: 9:02.5,9:05,9:07.5,...,9:30

    Last: 9:03,9:06,9:09,...,9:30

    First and Last every 6 min

    so it will be 6,12,18,24,30

    and second will light every 5min(round),

    [6,5]=30

    so they will be light every 30min

    and your answer is 9:30

    Source(s): my mind!!!
  • lastrick
    Lv 5
    2 decades ago

    Essentially, with problems like this, you're looking for the lowest common multiple (LCM). For 2 and 3, it's six (and implicitly an integer). Therefore, the second light is only of interest every 5 minutes. The LCM of 6 and 5 is 30. So, as stated above, 9:30 am would be next.

  • John C
    Lv 5
    2 decades ago

    9:30

  • godsladydi
    2 decades ago

    9:30a

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