Question

Please help.
A basketball player has a 50% chance of making each free throw. What is the probability that the player makes at most nine out of eleven free throws?

Answer 1

The number of throws that the player make X follows binomial distribution.

The probability that the player makes x throws out of eleven throws is

$P(X=x)=C(x,11)0.5^x(0.5)^{11-x}=C(x,11)0.5^{11}$

The probability that the player makes at most nine out of eleven free throws

is

$\sum_{x=0}^9C(x,11)0.5^{11}=1-\sum_{x=10}^{11}C(x,11)0.5^{11}\\ =1-C(10,11)0.5^{11}-C(11,11)0.5^{11}=1-\frac{12}{2^{11}} \\ =1-\frac{3}{512} =\frac{509}{512}$

Correct choice is (B).