Multiplying together 2-digit numbers in cases where the tens digits are the same and the ones digits added together equal 10

To multiply together 2-digit numbers in cases where the tens digits are the same and the ones digits added together equal 10:     ex. 12×18=216

-The tens digits of the numbers being multiplied are the same. Multiply this digit times its next higher number. This yields the hundreds digit(s) of the answer.    ex.  In (1,2,3,4…) the next higher digit to 1 is 2, so 1×2=2 for an answer of 2_ _.

-The ones digits of the numbers being multiplied could be added together to equal 10.  Multiply these ones digits together. This yields the last two digits of the answer.     ex.  2×8=16 for an answer of _16.

Check that   83×87=7221    54×56=3024    65×65=4225    71×79=5609    32×38=1216    93×97=9021    104×106=11024    112×118=13216

 

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