In a shipment of 20 computers, 3 are defective. two computers are randomly selected and tested. what is the probability that both are defective if the first is not replaced after being tested?
You have to use the multiplication rule. The probability that the fisrt one is defective: 3/20 And the probability that the second one is also defective and you can not replace the first computer drawn is: 3/20*2/19 = 3/190 = 0.0158
