SOLUTION: If​ P(A and ​B)equals0.3​, ​P(A)equals0.7​, and ​P(B)equals0.5​, find​ P(A or​ B).

Algebra ->  Probability-and-statistics -> SOLUTION: If​ P(A and ​B)equals0.3​, ​P(A)equals0.7​, and ​P(B)equals0.5​, find​ P(A or​ B).      Log On


   

Question 1149014: If​ P(A and ​B)equals0.3​, ​P(A)equals0.7​, and
​P(B)equals0.5​, find​ P(A or​ B).
Answer by math_helper(2461) About Me  (Show Source):
You can put this solution on YOUR website!
P(A or B) = P(A) + P(B) - P(A and B)

You have the numbers for the right hand side...


It may seem strange to subtract P(A and B), but if you'll notice each of P(A) and P(B) includes P(A and B) (draw Venn diagrams to help see this), then you realize P(A and B) is counted twice. One P(A and B) must be subtracted to compensate for this overcounting.