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An exam question

  1. May 10, 2005 #1
    I just wrote my senior school certificate exam ,but could not solve one of the maths questions .the question is as follows
    3 night quard a,b,c blow their their whistle at intervals 8,15,and 18 minutes respectively.if they blow together at 11.00 p.m,when next are they expected to blow together
  2. jcsd
  3. May 10, 2005 #2


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    8= 2*2*2, 15= 3*5, and 18= 2*3*3. The least common multiple of those is
    2*2*2*3*3*5= 360 which is 6*60 or 6 hours. They will all blow their whistles together again at 11+ 6 hours or 5:00 a.m.
  4. May 10, 2005 #3
    I dont not get it ,on wat principle of maths or wat branch is this on
  5. May 10, 2005 #4
    Lowest common multiples and greatest common factors.
  6. May 11, 2005 #5


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    The "branch of mathematics" is arithmetic!
  7. May 11, 2005 #6


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    Yes it's just a lowest common multiple question. Basically you need to have every prime factor from each number repeated to the maximum power that it appears in any of the individual numbers.
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