Well a perfect square looks like this:
6 x 6
2 x 2
So the number 72 is between the PRODUCT of two perfect squares such as those.
One product has to be above 72, and the other below it.
So lets multiply.
8 x 8 = 64
9 x 9 = 81
Oh look at that, 72 is between 64 and 81.
