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MENTAL MATH: TiPs & TrIcKs for...

Multiplication I

When you want to multiply two numbers ranging from 2 - 8, I'm sorry to say that you just have to learn those the hard way! No tricks!!

But when it comes to multiplying by 9, you just have to use your hands.

 

 
     

When multiplying any number times 9, to obtain the result, open your hands with your palm facing downwards. (This one is great for kids!)


(fig 8a)

 For example: 3 x 9 = 27. Put down the finger from left to right, equal to the number your multiplying.  In this case it would be your 3rd finger or middle finger of your left hand.

 
 

 


(fig 8b)

Notice that you have 2 fingers, a space, and then the other 7 fingers.... do these numbers ring a bell?

Now lets try it with 6 x 9 = 54 (Put down your 6th finger or right hand thumb).


(fig 8c)

Another cool trick is to write 4 columns. Column A with numbers from 1 - 10, column B with 9's. AB represent the operation. Now here comes the fun part. In column C write, the numbers from 0 - 9 and in column D write them from 9 - 0. See the results? 

A         B          C  D

1    x    9    =    0  9
2    x    9    =    1  8
3    x    9    =    2  7
4    x    9    =    3  6
5    x    9    =    4  5
6    x    9    =    5  4
7    x    9    =    6  3
8    x    9    =    7  2
9    x    9    =    8  1
10   x    9    =    9  0

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