Question

In a survey, 50 people use A, 40 use B, 30 use C, 15 use both A and B, 10 use both B and C, 8 use both A and C, and 5 use all three. Find the number who use at least one service.

Solution

1. Use the three-set union formula.
2. Total = 50 + 40 + 30 - 15 - 10 - 8 + 5.
3. Therefore, 92 people use at least one service.