Question

Suppose 80% of people can swim. Suppose 70% of people can

whistle. Suppose 55% of people can do both. What percentage of people
can swim or whistle?

Answer 1

95%

Explanation:

Let the proportion who can swim be denoted by P(S) while the proportion that can whistle be denoted by P(W)

The proportion that can swim and whistle will be P(S and W)

The proportion that can swim or whistle will be P(S or W)

To get the proportion that can swim or whistle will be P(S or W), we use

P(S or W)=P(S)+P(W)-P(S and W)

Given that P(W) is 70%, P(S) is 80% and P(S andW) is 55% then

P(S or W)=80%+70%-55%=95%