Question

Use the given information to find the indicated probability. a and b are mutually exclusive. p(a) = .8, p(b) = .1. find p((a ∪ b)').

Answer 1

If $A$ and $B$ are mutually exclusive, then

$\mathbb P(A\cup B)=\mathbb P(A)+\mathbb P(B)=0.8+0.1=0.9$

Then $\mathbb P((A\cup B)')=1-\mathbb P(A\cup B)=0.1$.