Question

Which numbers use only 2's and 5's as prime factors.

The numbers are 3,4,7,8,12,13,15,16,20,25,28,30,36,40,45,and 48.

Answer 1

The ones that are divisible by 10, and not 3. That would be 20 and 40. There are others that use JUST 2's (4,8 and 16) or just 5's (25).