prob(defect) = 3/12 = 1/4
prob(working) = 3/4
prob (5 of 5 are working)
= C(5,5) (3/4)^5 (1/4)^0
= 243/1024
prob(3 work, 2 don't work)
= C(5,3)(3/4)^3 (1/4)^2
= 10(27/64)(1/16)
= 270/1024
A manufacturer of calculators would like to separate defective calculators from calculators that are
acceptable. Through an error, a shipment of twelve calculators is sent out containing three defective
calculators and nine working calculators. A customer buys five of these calculators, without testing them.
a) What is the probability that all five will be acceptable?
b) What is the probability that two will be defective and three acceptable?
Thanks for your help
1 answer
1 answer