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Identify the balls

  1. Aug 29, 2008 #1
    On a Christmas tree there were two blue, two red and two white balls. All seemed the same, however in each colour pair one ball was heavier. All three lighter balls were the same weight, just like all three heavier balls.
    Using a pair of scales twice, identify the lighter balls.
  2. jcsd
  3. Sep 2, 2008 #2


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    Put in one scale a white and a red ball and in the other scale a blue and the other white ball.
    If the scales are even, this means that one of the colored balls is heavy and the other is light. Weight one against the other to determine which is which. The light white ball is the one that was in the same scale with the heavy colored ball.
    If the scales are not even, you know already that the heavy white ball is the one in the down scale. The colored balls may be both heavy, both light or the one in the down scale is heavy and the other is light.
    Put the two colored balls in one scale and the two white balls in the other. If the colored balls go down is because they are both heavy, if they go up, both are light, if the scales are even, the one that was down in the first weighting is heavy and the other is light.
  4. Sep 2, 2008 #3
    U R Right.
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