
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 (1p), or 3/5.
Richard Wurdack
Tuesday, December 31, 2002
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