Find the indicated probability

Question

If P(A or B)=0.07, P(A)=0.4 , and P(A and B)= 0.25, find P(B)

Answer 1

I think that P(AUB) should be 0.7, not 0.07.  Re-check your problem statement.   Whatever it is, the formula you need to use is:

 

     P(AUB) = P(A) + P(B) - P(A∩B)

 

     0.70 = 0.4 + P(B) - 0.25

 

Solve for P(B)

Answer 2

P(A or B) = P(A) + P(B) - P(A and B)

 

.7 = .4 + P(B) - .25

 

P(B) = .55