Question

Which pair of numbers has the same gcf as that of 48 and 78

A)4 and 34
B)8 and 18
C)9 and 15
D)12 and 30

Answer 1

greatest common factor is found by finding the factors of each
factors48=2 times 2 times 2 times 2 times 3
78=2 times 3 times 13
find common group
comon group=2 times 2=6
gcf=6
find others
narrow it down by crossing out any choices with numbers not divisible by 6
(crosses out A,B,C since A has 4 and B has 8 and C has 9)

therefor the answer is D, 12 and 18
check
12=2 times 2 times 3
18=2 times 3 times 3
common group=2 times 3=6
correct

answer is D, 12 and 18