Problem:
On a checkerboard composed of unit squares, what is the probability that a randomly chosen unit square does not touch the outer edge of the board?
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Answer Choices:
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E.
Solution:
The checkerboard has unit squares. There are unit squares on the outer edge, and unit squares in the interior. Therefore the probability of choosing a unit square that does not touch the outer edge is .
There are unit squares in the interior. Therefore, the probability of choosing a unit square that is does not touch the outer edge is .
Answer: .
The problems on this page are the property of the MAA's American Mathematics Competitions