A survey of 120 teachers determined the following: 70 had high blood pressure, 40 had heart trouble, 30 had both high blood pressure and heart trouble What percent of the teachers surveyed had neither high blood pressure nor heart trouble?
Of the 40 who had heart trouble, 20 also had high blood pressure, so there are 40-20=20 teachers who only have heart trouble. Similarly, there are 70-20=50 teachers with only high blood pressure. So, of the 120 teachers total, there are 20+20+50 teachers with one of these two. That means 120/90=30 teachers with neither, which is 25% of the teachers.
