2 probability question

#1
I have just recently been learning probability and I have been having troubles with some questions. If someone can help me on these two question, I would appreciate it.

1. A basketball player has a success rate of 80% for shooting free throws. What is the probability she will make atleast three out of 5 attempts.

2. A person is chosen at random from shoppers at a store. If the person's probability of having blonde hair and glasses is 2/25 and the probability of wearing glasses is 9/25, determine P(blonde hair|wears glasses).
The only thing I could do is do a venn diagram for this question and I'm not too sure if it's even right. Please reply if you know how to do these two questions.

Thanks
 

JohnM

TS Contributor
#2
Problem 1 uses the binomial probability distribution. Check our Examples section - we have similar problems there.

p = 0.8
q = 1-p = 0.2
n = number of trials = 5
r = number of successes = at least 3 = 3 or 4 or 5

Problem 2 uses the concept of conditional probability, and by definition:

P(A|B) = P(A and B) / P(B)

event A = blonde hair
event B = glasses
P(A and B) = 2/25
P(B) = 9/25