To multiply together 2-digit numbers in cases where the tens digits added together equal 10 and the ones digits are the same: ex. 21 x 81 = 1701
-Multiply the ones digits of the numbers being multiplied. This yields the last two digits of the answer. ex. 1 x 1=_ _01
_Multiply the tens digits of the numbers being multiplied, and to this add the common ones digit of the numbers being multiplied. This yields the first 2 digits of the answer. ex. (2 x 8) + 1 = 17_ _
Prove these: 39 x 79 = 3081 42 x 62 = 2604 35 x 75 = 2625 34 x 74 = 2516