Question

If P (A|B) = 0.5, P (A) = 0.45 and P (B) = ?

Answer 1

Bayes' theorem:

$P(A|B)=\frac{P(B|A)P(A)}{P(B)}$

then:

$P(B)=\frac{P(B|A)P(A)}{P(A|B)}=\frac{0.45P(B|A)}{0.5}=0.9P(B|A)$