Question:
If A and B are two events associated with a random experiment for which P(A) = 0.60, P(A or B) = 0.85 and P(A and B) = 0.42, find P(B).
Solution:
Given : P(A) = 0.60, P(A or B) = 0.85 and P(A and B) = 0.42
To find : P(B)
Formula used : $P(A$ or $B)=P(A)+P(B)-P(A$ and $B)$
Substituting in the above formula we get,
$0.85=0.60+P(B)-0.42$
$0.85=0.18+P(B)$
$0.85-0.18=P(B)$
$0.67=P(B)$
$P(B)=0.67$