For which pairs of numbers is 6 a common factor?
choose all answers that are correct.
a.) 12 and 20
b.) 18 and 24
c.) 30 and 54
d.) 42 and 56

Commen factor means you can get integers after division.

A. 20 is not correct

B. Correct

C. Correct

D. 56 is not correct

Easy way is to list multipules of 6
6,12,18,24,30,36,42,48,54
so we can see that A doesn't work because 20 doesn't have 6 as a common factor
C works
D doesn't work because of the 56

answers are B and C

another way is to factor each
notice that 6=2*3
so factor each and see if we can find a 2*3 in each

A.
12=2*2*3, so there is a 6
20=2*2*5, not 6

B.
18=2*3*3, so there is a 6
24=2*2*3*3, so there is a 6
works

C.
30=2*3*5, there is a 6
54=2*3*3*3, there is a 6
works

D.
42=2*3*7, there is a 6
56=2*2*2*7, there isn't a 6
nope

answes are B and C