Question

The probability of event A occurring given that event B has already occurred is 0.61. The probability of both events occurring is 0.5. What is the probability of event B occurring?

a) 0.305
b) 0195
c) 0.390
d) 0.820
e) 0.500

Answer 1

D. 0.82

Explanation:

P(A|B)= 0.61

P(A∩B)= 0.5

P(B)=?

The conditional probability formula is:

P(A|B)=P(A∩B)/P(B)

Then, you must transform this formula to get P(B):

P(A|B)*P(B)= P(A∩B)

P(B)= P(A∩B)/P(A|B)

P(B)= 0.5/0.61

P(B)= 0.819

P(B)= 0.82