Use a factor tree. 9 3,3 16 8,2 4,2,2 2,2,2,2
factor tree of 216
The prime factor tree of 280 is:140,270,2,235,2,2,27,5,2,2,2
Factor Tree of 20: ........20 ......../ \ .......4 5 ....../ \ .....2 2
A tree.
9 3,3
9 3,3
9 ^ 3x3
9 3,3
9 3,3
9 3,3 54 27,2 9,3,2 3,3,3,2
63 ^ 7*9 ^ 3*3
In the case of 27, there is only one possible factor tree - using the factors 3 and 9 as the first step. 27 3 x 9 3 x (3x3)
9 3,3 18 6,3 2,3,3 The GCF is 9.
18 9 2 33 3 2
99 9, 11 3, 3, 11
27 3, 9 3, 3, 3