If r and s are distinct prime numbers, which of the following CANNOT be evenly divisible by rs?
6
8
10
15
18
(FROM KNEWTON PREP)
6
8
10
15
18
(FROM KNEWTON PREP)
It is the only one that does not have at least 2 different prime factors
6 = 2x3
8 = the answer 2x2x2
10 = 3x5
15=3x5
18=2x3x3
