Question

in a set of 30 different positive integers, every number is even and/or a multiple of 3. if 22 of these numbers are even and 15 are multiples of 3, then how many of these numbers are multiples of 6?
a. 23
b. 22
c. 15
d. 11
e. 7

Answer 1

A = even
B = multiple of 3
A and B = multiple of 6
|A or B| = |A| + |B| - |A and B|
30 = 22 + 15 - |A and B|
|A and B| = 7