Read this from the
omy. Actually this is simple algebra.
(10+a)(10+b) = 100 + 10x(a+b) +a*b
or
(100-a)(100-b)=10000-100x(a+b)+a*b
I would like to share with you a more interesting way of doing 'times', which is called the Russian multiplication. What we need to do is keep halving the first no. and keep doubling the second no.
Take 19x6=114 as an example.
19 6
9 12
4 24
2 48
1 96
Then cross out the entire row of the
even number in the first (halve) column.
Add all the remaining number in the second column will give you the product.
6+12+96=114
This method can apply to any digits nos.
Take another example 19x19=361
19 19
9 38
4 76
2 152
1 304
The answer of 19x19 = 19+ 38 +304 =361
Keep reading only if you are interested. 😁