Question

A survey was given to 339 people asking whether people like dogs and/or cats.

190 said they like dogs
141 said they like cats
88 said they don't like cats or dogs.

How many said they liked both cats and dogs?

Answer 1

80.

Explanation:

Let
`C` be the set of people who like cats and
`D` the set of people who like dogs. Under the cardinality theorem you have

n(CUD) = n(C) + n(D) - n(CnD)[/tex], isolating the
`(C`∩
`(D` , you have n
`(C`∩
`(D` = n(C) + n(D) -
`(C`∪
∩
`(D`
`= 190 +141 -251 = 80`