## Saturday, February 9, 2008

### Speed and Power: Multiplying Numbers with the Same Ending...

Jagadguru Swami Sri Bhārati Kŗşņa Tīrthaji Mahāraja showed through Nikhilam Navatascaram Dasatah that you can instantly multiply numbers using a base number. Lets say we are trying to multiply 18 X 13. Here if we use 10 as our base, and we find the deviation of the numbers from the base, the rest is so easy to calculate.

18 : deviation from base = 8
13 : deviation from base = 3

Now, we cross-add one of the deviations to the number, for instance, 18 + 3. Either way we get 21. That will be our left most number. Now we multiply the deviations, 8 X 3, to get 24. Now since we are using base 10, we leave 4 (from the 24) as the right most number and carry the 2 to the left most number, which is 21. So we get [21 + 2].[4] = 234!

This is explained quite thoroughly in other websites and posts, especially here.

But if that intrigued your interest, how about if we try something else? Lets say we have two numbers, both end with the same number, lets say 23 and 13.

If we want to quickly (and mentally) multiply the numbers, just do this 3 step process:

1. Square the ending number to get the the right-most number of the answer: in this case its 9
2. Add the two first numbers together, (2 + 1) and multiply it with the ending number (3): in this case its 3 X 3. This gives us the middle number, which is 9.
3. To get the left-most number, just multiply the first numbers together, in this case (2 X 1), to get 2.