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A shipment of 40 television sets contains 3 defective units. How many ways can a vending company can buy five?

A shipment of 40 television sets contains 3 defective units. How many ways can a vending company can buy five of these units and receive no defective units. How would you go about solving this?

Public Comments

1. He first turns on 5 TVs. If they all are good, he quits. If there are one or more defective units he selects another set. If he now has 5 good ones he quits. If not he picks a seventh set. If he now has 5 good sets he quits. Otherwise he has four good sets and three bad sets so all of the rest are good and he just picks up one of them. Now he must have five good set. Of course he could just turn on eight sets while the first one is still warming up and he has to have five or more good sets. .