Question

How many positive integers less than 2018 are divisible by 20 or by 25, but not by both?

Answer 1

160

Explanation:

Divisible by both 20 and 25:

Divisible by 100

2018/20 = 100.9

100 multiples of 20

2018/25 = 80.72

80 multiples of 25

2018/100 = 20.18

20 multiples of 100

Union: 100 + 80 - 20

160