Question

Which is the greatest common factor of 16 and 40?

A- 4
B- 8
C- 40
D- 80

Answer 1

8 because it's the highest number that can go into both numbers evenly.

Answer 2

16 = 4*4 = 2*2*2*2 
40= 5*8 = 5*2*2*2

2*2*2 = 8 is the common part of 16 and 40, so 8 is the greatest common factor of 16 and 40.

Answer is B. 8.