Describe a Venn Diagram.
Not all uses of Venn Diagrams involve logic. Here is an example of a counting problem that cand be solved with a Venn Diagram:
A survey of 100 people shows that 50 like apples, 60 like bananas, and 20 like both. Based on that information, can you determine how many don't like either one?
This problem looks like a trick, but you need to read carefully to understand how it works.