### Brain Teasers

# Tennis Balls 2

You have 27 tennis balls. One is heavier than all the others, which all weigh the same. Using the scale which you have, what is the minimum amount of weighings you must make to determine with all certainty which is the heavier tennis ball?

### Hint

Think about grouping the tennis balls...### Answer

You only have to use the scale 3 times:First, divide the balls into three groups of nine each.

Then, weigh two of the groups on the scale separately. If there is a large difference, then the heavier group has the heavier ball in it. If they are the same weight, then the third group must have the heavier ball in it.

Third, divide this group into three smaller groups of three tennis balls each. Again, weigh two of them separately.

Once you have identified the cluster of tennis balls with the greatest weight, for the third time compare two of the tennis balls. Using the logic as in the first and second steps, you can now define the heaviest tennis ball!

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