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One more version of the "nine thing"....
To find the product of 9 times any single digit X greater than 1, simply subtract 1 from X and place the result in the tens place while placing the difference between the tens place value and 9 in the ones place.
For example, with X=8....
9 * 8 = _ _
(8-1=7)
9 * 8 = 7 _
(9-7=2)
9 * 8 = 72
Not sure why I always found this one interesting/useful. Perhaps it is because I have a hard time memorizing certain things and used this to get through my multiplication tables back in 3rd grade. Yes. It would seem that the formula would be harder to remember than the answers, but my memory has never quite worked that way.
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