The probabilities that stock A will rise in price is 044 and

The probabilities that stock A will rise in price is 0.44 and that stock B will rise in price is 0.56. Further, if stock B rises in price, the probability that stock A will also rise in price is 0.13

What is the probability that at least one of the stocks will rise in price?

Solution

if stock B rises in price, the probability that stock A will also rise in price is 0.13-
so,
0.13 = P(A intersection B)/P(B)
=> P(A intersection B) = 0.13*0.56 = 0.0728

so,
P(AUB) = P(A)+P(B)-P(A intersection B) = 0.44+0.56-0.0728 = 0.9272