# If A and B are mutually exclusive events,$P(A)=0.35$ and $P(B)=0.45$ find P(B')

$\begin{array}{1 1}(A)\;0.55\\(B)\;0.45\\(C)\;0.65\\(D)\;0.85\end{array}$

Toolbox:
• $P(B')=1-P(B)$
A and B are mutually exclusive events.
$\therefore P(A \cap B)=\phi$
$P(B)=0.45$
$P(B')=1-P(B)$
$\qquad\;=1-0.45$
$\qquad\;=0.55$
Hence (A) is the correct answer.