department selects a random sample of 4 of the motors.

(a) What is the probability that exactly 3 of the motors in the sample are defective?

(b) What is the probability that at least one of the motors in the sample is defective?

Im pretty sure the answers are this:

a) 0.012304284, which is 1.2 % ( To get this I choose 3 from the defective, and one good item, which is (10/3) times (50/1) divided by (60/4) (since that was the total batch of motors, and you choose a sample of 4)

b) 0.000020507, because you do (10/1) times (50/0) to get 10, then you take 10 and divide it into (60/4).

Not 100% on if these right or not, but I think thats how you do it!