What is the GCF of 63 and 84-?

Answer 1

21

21 is the only positive integer that exhibits the Perfect Progression where if the multiples of 21 up to 210 are placed in to two parallel vertical columns so that the first reads 2, 4, 6, 8, 10 etc and the second 1, 2, 3, 4, 5 etc for example,

2 1

4 2

6 3

8 4

10 5

whereby each in one column multiplied by another number ordered diagonally in the other column equals the multiplication of the opposite diagonal, for example, 2x2 and 1x4 both equal 4, then both opposite diagonal numbers 4x3 and 2x6 equal 12, then both opposite diagonal numbers 6x4 and 3x8 equal 24 and so on.

Answer 2

The GCF is 21.

Answer 3

GCF(84, 63) = 21.