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Probability 6.0/10

Coin on the Tiles

A floor is covered with square tiles of side 1, separated by grout lines of negligible width. A coin of diameter 1/3 is tossed onto the floor so that its centre is uniformly distributed over the tile it lands on. What is the probability that the coin lies entirely inside a single tile, touching no grout line? Give a reduced fraction.

Related problems & prerequisites

Worth solving first

Source: Classic carnival-game exercise in geometric probability, in wide circulation; no traceable original source. Statement written for AxiomIQ.