Probability question: A spaceman's supply of oxygen comes from two independent sources.

Question

A spaceman's supply of oxygen comes from two independent sources. Source A has probability 0.9 of working, and Source B has probability 0.8 of working. What is the probability that at least one of the sources is working?

Answer 1

P(A will not occur) = 1 - 0.9 = 0.1

P(B will not occur) = 1 - 0.8 = 0.2

Since independent events

P(A will not occur and B will not occur) = 0.1 * 0.2 = 0.02

P(at least one of A and B will occur) = 1 - P(A will not occur and B will not occur) = 1 - 0.02 = 0.98