P(A)=0.6 P(A and B)=0.4 P(A or B)=0.7 P(B)=?

Question

P(A)=0.6 P(A and B)=0.4 P(A or B)=0.7 P(B)=?

 

What is the formula to find the probability of B?

Answer 1

Approach this by using a Venn diagram.

Place 0.4 in the leaf-shaped overlapping of circles A and B.

Since P(A) = 0.6, that leaves 0.2 to place in the other part of circle A.

Since P(A or B) = 0.7, that leaves 0.1 to place in the non-overlapping part of circle B.  

ANSWER: 0.1

 

Look in your notes and you will see a formula that applies to this case: P(A or B) = P(A) + P(B) - P(A and B)