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Trick to find product of two numbers | FullFunCity
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Trick to find product of two numbers

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Trick to find Product of two 2-digit numbers quickly.

 

It is easier to get results when the numbers are not too far apart and their difference is even, for example , let one number be 30 and the other be 28.

1. Find their average : (28 + 30)/2 = 29 ;
2. Half the diffetrence : (30 – 28)/2 = 1 ;

3. Subtract the squares : 30 x 28 = 29² – 1² = 840

 

The ancient Babylonian used the similar approach. They calculated the sum and the difference of the two numbers, subtracted their squares and divided the result by four. For example,
Steps used in this method:
1. Calculate the sum of the two numbers.
2. Calculate the difference of the numbers.
3. Subtract the squares of the results obtained and divide the result by 4.

Example :

33×32 = (65² – 1²)/4
= (4225 – 1)/4
= 4224/4
= 1056.

Example :
Let the numbers be , 30 and 28.

30 + 28 = 58
30 – 28 = 2
So, 30 x 28 = (58² – 2²)/4 =  840

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