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 five-year period. What is the maximum tolerable probability of failure for each relay?

Answer 1

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

Answer 2

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%

Answer 3

H.C as this does give the right answer maybe or maybe not by coincidence,
the exact way of getting the answer would be
0.9 = x^8
x = (0.9)^(1/8)
x = 0.98691628136...