81 multiply 99

Question

Solving steps of math I don't know it

Answer 1

First memorize your multiplication tables up to 10 at least.

81*99

81*100=8100      (there is one group of 81 too many)

8100-81=8019     (subtract this extra group of 81)

Answer 2

Break it down:

80 * 90 + 80 * 9 + 1 * 90 + 1 * 9