Data Management
posted by May .
A critical circuit in a communication network relies on a set of eight identical relays. If any one of the relays fails, it will disrupt the entire network. The design engineer must ensure a 90% probability that the network will not fail over a fiveyear period. What is the maximum tolerable probability of failure for each relay?

the answer is supposed to be 1.3 % but i don't know how this solution is reached.

P(A) = 0.90 [not failing]
P(b) = 1  0.90
= 0.10 [failing]
Answer: 0.10/8
= 0.0125
Multiply that to get 1.25 or 1.3%