Question

One common factor of two numbers is 40. Another common factor is 10. If both numbers are less than 100, what are the two numbers?

Answer 1

Only two numbers less than 100 have a factor of 40: 40 (1 x 40) and 80 (2 x 40). Since 40 is a factor of both 40 and 80, 10 must also be a factor - indeed, 40 = 4 x 10 and 80 = 8 x 10.

The two number must be 40 and 80.