Suppose S and T are mutually exclusive events. Find P (S or T) if P (S) = 65% and P (T) = 7%.

P (S∪T) = 34

Explanation:

We use the following fundamental definition from Probability and Set Theory:

P (A∪B) = P (A) + P (B) - P (A∩B)

And if we apply this to our problem we have:

P (S∪T) = P (S) + P (T) - P (S∩T)

= 13 + 512 - P (S∩T)

= 34 - P (S∩T)

Now we are told that S and T are mutually exclusive, and so:

P (S∩T) = 0

Hence,

P (S∪T) = 34