A P/OM student has purchased a four-function calculator for use during exams.This calculator is perfectly reliable except for two parts: its microchip,which has a failure rate of one in every twenty hours of operation; and its battery,which has a failure rate of one in every ten hours of operation.Also,on average the battery will fail in five hours,with a standard deviation of 30 minutes.Assuming that a new battery has just been installed,what is the probability that the calculator will perform reliably during a one-hour exam?
A)0.800
B)0.855
C)0.900
D)0.950
E)1.850

Question

Quizplus · Accepted Answer

The probability of the calculator performing reliably is the product of the probabilities of both the microchip and the battery not failing. The microchip has a failure rate of 1/20 (or 0.05), so the probability of it not failing is 1 - 0.05 = 0.95. The battery has a failure rate of 1/10 (or 0.10), so the probability of it not failing is 1 - 0.10 = 0.90. Multiplying these probabilities gives 0.95 * 0.90 = 0.855.

A P/OM Student Has Purchased a Four-Function Calculator for Use