To multiply together 2-digit numbers in cases where the tens digits added together equal 10 and the ones digits are the same: ex. 21×81=1701

-Multiply the ones digits of the numbers being multiplied. This yields the last two digits of the answer. ex. 1×1=_ _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. (2×8)+1=17_ _

Prove these: 39×79=3081 42×62=2604 35×75=2625 34×74=2516

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