Permutations HELP

Question

 Rework problem 30 from the Chapter 2 review exercises in your text, involving basketballs with defective valves. For this problem, assume the bag contains 16 basketballs, 6 of which have defective valves. You choose 2 out of the bag randomly.

What is the probability that at least 1 will have a defective valve?

Answer 1

The Probability that the first one you pick is not faulty is 24/30. If you did, pick a faulty one, there are 29 left and the probability of picking a good one is 23/29. so the probabilty of picking 2 good ones is (24*23)/(30*29). The probablility that at keast one is defective is 1- (24*23)/(29*30). This is sometimes called sampling without replacement.