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cars on the road

Let p be the probability that you will *not* see a car in 5 minutes.

The probability that you will *not* see a car in 20 minutes is p^4.

The probability that you *will* see a car in 20 minutes is 1 - p ^4.

Solving for p then, we have

609/625 = 1 - p^4

16/625 = p^4

p = (16/625)^(1/4)

p = 2/5

Since p is the probability that you will *not* see a car in 5 minutes, the answer to the question is (1-p), or 3/5.

Richard Wurdack
Tuesday, December 31, 2002

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