11-01-2009, 06:38 PM
When multiplying by 5's dive the number by 2 and multiply by 10. For example:
8 x 5 = 40
HOW?
8 / 2 = 4.0
4.0 x 10 = 40
When multiplying by 9's subtract 1 from the first digit(This is the first digit of the answer) then subtract that number from 9(This is the second digit) For example:
7 x 9 = 63
HOW?
7 - 1 = 6
9 - 6 = 3
8 x 5 = 40
HOW?
8 / 2 = 4.0
4.0 x 10 = 40
When multiplying by 9's subtract 1 from the first digit(This is the first digit of the answer) then subtract that number from 9(This is the second digit) For example:
7 x 9 = 63
HOW?
7 - 1 = 6
9 - 6 = 3