How Likely is Just Four?
A toll road expects an average of 7 customers every 10 minutes.
What is the probability that, in the 10 minute interval, the toll road has exactly 4 customers? Multiply your answer by 100 and round. (You can use a calculator.)
The answer is 9.
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2 solutions
Nice job @Prince Loomba ! Congratulations being the first one to get it, too.
To solve, we can use the Poisson Distribution: p ( x ; μ ) = x ! μ x ⋅ e − μ . Where μ is the average interval and x is the occurrence within the interval we are finding. So the probability is: 4 ! 7 4 ⋅ e − 7 = 2 4 2 4 0 1 ⋅ e − 7 = 2 4 2 4 0 1 ⋅ e 7 1 ≈ 0 . 0 9 1 2 . We multiply 0 . 0 9 1 2 by 100 and round to get 9 .
Same approach. e^-7*7^4/4!=0.0912