The functioning of a particular machine is dependent on two safety valves: A and B. The machine will operate fine as long as one of the safety valves is functioning properly. Valve A has a 10% chance of failure while valve B has a 5% chance of failure. What is the probability that the machine will NOT break down?
A) 92%.
B) 95%.
C) 99.5%.
D) 6%.

Question

Quizplus · Accepted Answer

The probability of valve A functioning properly is 90% (100% - 10%), and the probability of valve B functioning properly is 95% (100% - 5%). The probability of both valves failing simultaneously is 0.10 * 0.05 = 0.005 or 0.5%. Therefore, the probability of the machine not breaking down (at least one valve working) is 100% - 0.5% = 99.5%.

The Functioning of a Particular Machine Is Dependent on Two