[abuddy]

The trick is to remember the product of every number multiplied by itself and go from there.

It's easier for me to know that 7x7 is 49 or that 8x8 is 64. Then I either go up or go down. If asked what the sum of 7x8 is I remember that 7x7 is 49 and add 7 to it or remember that 8x8 is 64 and substract 8 from 64.