Question

A survey of 140 freshmen business students at a local university produced the results listed below. How many students took only psychology?
33 took history;
42 took science;
39 took psychology;
19 took history but not science;
12 took science and psychology;
10 took history and psychology;
2 took all three

Answer 1

15

A total of 39 took psychology. 12 of those took that and science and another 10 of those took that and history. 2 people took all three. 12+10+2 = 24 students who took psychology along with another class. To find the number of students who took ONLY psychology, you would take 39 and subtract 24, which leaves you with 15.