Multiplying two 2-digit numbers

steps

1. Both numbers should have the same second digit.
2. Choose first digits whose sum is 10.
3. Multiply the first digits and add one second: X X _ _.
4. Multiply the second digits together: _ _ X X.

Example:

1. If the first number is 67, choose 47 as the second number (same second digit, first digits add to 10).
2. Multiply the 1st digits, add one 2nd.
   6x4 = 24, 24+7 = 31. 3 1 _ _
3. Multiply the 2nd digits. 7x7 = 49 _ _ 4 9
4. So 67 × 47 = 3149.

See the pattern?

1. If the first number is 93, choose 13 as the second number (same second digit, first digits add to 10).
2. Multiply the 1st digits, add one 2nd. 9x1 = 9, 9+3 = 12.
   1 2 _ _
3. Multiply the 2nd digits. 3x3 = 9 _ _ 0 9
4. So 93 × 13 = 1209.