• 75² = 5625

  75² means 75 x 75.
  The answer is in two parts: 56 and 25.
  The last part is always 25.
  The first part is the first number, 7, multiplied by the number "one more", which is 8:
  so 7 x 8 = 56
  

• Similarly 85² = 7225 because 8 x 9 = 72.

Method for multiplying numbers where the first figures are the same and the last figures add up to 10.

• 32 x 38 = 1216

Both numbers here start with 3 and the last
figures (2 and 8) add up to 10.

So we just multiply 3 by 4 (the next number up)
to get 12 for the first part of the answer.

And we multiply the last figures: 2 x 8 = 16 to
get the last part of the answer.

Diagrammatically:


• And 81 x 89 = 7209

We put 09 since we need two figures as in all the other examples.