The sets A and B in Exercise 5.
The following formula gives the probability of the union of any two events, whether or not they are disjoint,
Pr(A ‹ƒ B) = Pr(A) + Pr(B) - Pr(A ‹‚ B).
As indicated in the figure, adding the area in A and B counts the area in the intersection A ‹‚ B twice. Subtracting the area of the intersection corrects for this double counting.

Test this formula on the above example.

Transcribed Image Text:

A n B counted twice