Jeff W. answered 10/06/15
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Both of these questions can be answered with the Binomial Probability formula:
nCr * p^r * q^(n-r)
p is the probability of success (meaning the player makes a given free throw)
q is the probability of failure (meaning the player misses a given free throw)
n is the number of free throws attempted
r is the number of free throws made
So for problem a, the probability of making exactly 5 shots out of 7 is:
P = 7C5 * (.84)^5 * (.16)^2 = .22483
And for problem b, the probability of making at least 6 shots is the probability of making exactly six PLUS the probability of making exactly 7:
P = 7C6 * (.84)^6 * (.16)^1 + 7C7 * (.84)^7 * (.16)^0 = .39345 + .29509 = .68854