99 = 100-1
999 = 1000-1 and so on.
So any number multiplied by 9 will be putting a zero at the end of the number and subtract the same number from it. If it is 99 put 2 zeros and subtract the number from it.
Ex. 48 X 9 = 480 - 48 = 432
345663 X 9 = 3456630 - 345663 = 3110967
34 X 99 = 3400 - 34 = 3366
23456 X999 = 23456000 - 23456 = 23432544
This method is applicable only for small numbers. Larger the number more difficult is the subtraction.
Now try the following multiplications
47 X 99 = ___
895 X 999 = ____
7643789 X 9999999999 = __________
For solving this type carefully read the following. Its very interesting.
47 X 99 = 4 6 5 3
The procedure is as follows
1. Subtract the given number with one and write it. (Here 46 = 47 - 1).
2. Then starting from the left side find the numbers obtained from subtracting it from 9 and write them next to the first obtained value.(Here the obtained value is 46. Start from 4. 4 needs 5 to reach 9 and 6 need 3. So write 5 and 3next to 46, i.e., 4653. OVER that's the answer.)
Ex. 895 X 999 = 894105
9876543 X 9999999 = 98765420123457 which even a calculator can hold. Try it in a calculator.
If the number of 9's to be multiplied is greater than the the number of digits in the number to be multiplied
371 X 9999 = 3 7 0 9 6 2 8
The method is same as above. The only thing we have to do is to put the extra number of 9's immediately after the step no. 1 and proceed with other steps too.
NOTE : This method is applicable only if the number of digits in the number to be multiplied is equal to or greater than the number of 9,s (Above we see 47 X 99, 4521 X 999999 etc)
