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Viki, Internet Researcher
Category: General
Satisfied Customers: 860
Experience:  I have eleven years experience writing statewide educational tests for all levels.
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There are 9 baseballs and 1 weighs more than the others. You

Customer Question

There are 9 baseballs and 1 weighs more than the others. You have a set of scales that you can use only twice. How can you tell which ball is heavier?
Submitted: 7 years ago.
Category: General
Expert:  Viki replied 7 years ago.
Hi

First, you must divide the balls into three groups of three.

Then, put one group on one side of the scale and another group on the other side. (Keep the third group off to the side.)

If the weights are in balance, then the heavier ball is in the group that you didn't balance. If one side of the balance weighs more, then the heavier ball is in that group.

Next, weigh any two of the three balls in the group that is heavier. If they are in balance, then the third ball that wasn't balanced in the group is the heavier one. If one side is heavier than the other, then the ball on that side is the heavier one.