If two events are mutually exclusive, why is P(A and B) =0?

A and B means those items that are in both A and B at the same time.

 

Mutually exclusive means if an item is in A it cannot be in B, and if an item is in B it cannot be in A.

 

So, if A and B are mutually exclusive there are no items that occur in both A and B.  

In other words p(A and B) = 0

.