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Doobie weigher

  1. Aug 17, 2004 #1
    There are nine doobies on a table of equal size but one of them contains hash which makes it weigh more than the other eight doobies. You have a balance beam scale in front of you that you can use weigh the doobies only twice. Determine the method of finding out which doobie contains the hash, using only two weighs.
  2. jcsd
  3. Aug 18, 2004 #2
    Weigh 123x456 .
    If 123 is the heaviest, then weigh 1x2 . If 1 equals 2 , pick 3 ; if not, pick the heaviest.
    If 123 is the lightest, then weigh 4x5 . If 4 equals 5 , pick 6 ; if not, pick the heaviest.
    If 123 equals 456 , then weigh 7x8 . If 7 equals 8 , pick 9 ; if not, pick the heaviest.


    I hope you have understood the Forty 1lb Weights' solution...
    Last edited: Aug 18, 2004
  4. Aug 18, 2004 #3
    BTW, take a look at the threads 'Nine Digit Numbers' and
    'I lost my calculator batteries in a flood' , too.

    I guess you've lost your calculator batteries... :smile:
    Last edited: Aug 18, 2004
  5. Aug 19, 2004 #4
    Roger that Rogerio. Sorry I am not a math guy. I try and try but ultimately I am stupid. The doctor forgot to catch me when I popped our of my mother and I landed head first. P.S. My lb. weight solution is correct I think, if you can only put weights on one scale end.
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