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Sunday, August 14, 2011

multiplying two numbers in the 90's (Insane math tricks)

Okay so everyone wants to do multiplication quickly right.  Well we all know how to multiply by 10, 1, 2,3,4,5,6,7,8, and even 9 but what about 90's.  Here is a trick to multiply numbers in the 90's quick and easy.
So take two numbers in the 90's let's say 94 and 97 we type it in on a calculator and get 9118 and here is how you can do it in your head.
STEPS
1. find the distance from 100 both numbers are. 94 is 6 and 97 is 3
2. add the distances together and you get 9
3. subtract that number from 100 and get 91 a.k.a the first two digits of the answer.
4.Take the two distances from step one and multiply them together and you get 18 a.k.a the last two digits of the number giving you the final answer 9118.
Use this on any other set of two numbers in the 90 to 99 range and i guarantee it will work.

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