Multiplying together numbers near 100

To multiply together numbers close to and below 100:   ex.  96×98=9408

-Subtract each number being multiplied from 100 and multiply these differences together. This yields the last two digits of the answer.    ex. 100-96=4    100-98=2       4×2=_ _ 08

-Add the differences above and subtract from 100. This yields the first 2 digits of the answer.     ex. 4+2=6    100-6=94_ _

*An alternate last step: You can take the difference from 100 of one number being multiplied and subtract this from the other number being multiplied (subtract because you are below 100).    96-2 and 98-4 give the same result as 100-(2+4). Either way is fine.

Try these:   93×97=9021       94×88=8272        97×97=9409

 

To multiply together numbers close to and above 100:    ex. 107×102=10914

-Follow step one above:    107-100=7      102-100=2         7×2=_ _ _14

-Begin step two above, adding the differences, but this time add this to 100. This yields the first three numbers of the answer.     ex.  (7+2)+100=109_ _

Try these:     109×111=12099     103×105=10815      112×112=12544

*An alternate last step: You can take the difference from 100 of one number being multiplied and add it to the other number being multiplied (add because you are above 100).   107+2 and 102+7 give the same result as (7+2)+100. Either way is fine.

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