A large stockpile of used pumps contains 20% that need repair. A repairman is sent to the stockpile of pumps with 3 repair kits. He selects pumps at random and tests them to determine if they need repair. If the pump works corretly, he goes on to the next pump. If the pump does not work, he repairs it with one of his repair kits. (a) Determine the probability that he uses his last repair kit after testing the 7th pump. (b) It takes 10 minutes to test a working pump and 30 minutes to test and repair a pump that is not working, find the expected amount of time that the repairman will need before he uses all 3 repair kits.

A large stockpile of used pumps contains 20% that need repair. A repairman is sent to the stockpile of pumps with 3 repair kits. He selects pumps at random and tests them to determine if they need repair. If the pump works corretly, he goes on to the next pump. If the pump does not work, he repairs it with one of his repair kits. (a) Determine the probability that he uses his last repair kit after testing the 7th pump. (b) It takes 10 minutes to test a working pump and 30 minutes to test and repair a pump that is not working, find the expected amount of time that the repairman will need before he uses all 3 repair kits.

A First Course in Probability (10th Edition)

10th Edition

ISBN:9780134753119

Author:Sheldon Ross

Publisher:Sheldon Ross

Chapter1: Combinatorial Analysis

Section: Chapter Questions

Problem 1.1P: a. How many different 7-place license plates are possible if the first 2 places are for letters and...

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