Help with hw question

Question

There are 30 quarts of milk on a supermarket shelf, 6 of which are spoiled. A customer buys five quarts of milk. a. How many samples contain exactly 3 quarts of spoiled milk?

b. How many samples contain at most 1 quarts of spoiled milk?

Answer 1

p = 6/30 = 1/5 = 0.2

q = 1-p = 0.8

(a) Binomial p=0.2, n=5, k=3

(5 choose 3) (0.2)^3 ( 0.8)^2 = 10 * 0.008 * 0.64 = 0.0512

(b) Binomial p=0.2, n-5 , k=0,1 -

(5 choose 1)(0.2)^1 ( 0.8)^4 = 5 * 0.2 * .4096 = 0.4096

(5 choose 0)(0.2)^0((0.8)^5 = 0,32768

total is 0.73728