Now this is useful...

Philip Goh theres another way. its kind of like factoring in algebra. lets take 24x57 for an example. what u do is u take the first digit of both numbers and multiply them together. u get 10. so u know the first part of the number must be 10. now, take the last digit of the first number and the first digit of the second number and multiply them together. u get 20. now take the first digit of the first number and the last digit of the second number and multiply them together. u get 14. take 20 and 14 and add them together. u get 34. but this number can only be one digit, so you carry the tens digit (3) and add it to the first part of the number (10). u get 13. so the number so far is 134_. to find the blank, you multiply the last digit of both numbers. u get 28. but u can only have one digit in this place, so carry the tens digit (2) and add it to the digit before (4). u get 6. the final number is 1368.

Excellent trick sir ji..hatsoff

21 × 31 one can choose a base of 20 or 30. So 21 - 30 =-9 and 31-30=1. 21+1= 31-9=22 and multiply this by 3 which gives 66. -9×1=-9 so it would be equivalent to 660-9=651

Nice trick sir !!! Thank You

45×73 can be done like this. I would use two bases 40 and 80.

This problem can be done but it's a little involved. We note 20 is a good base for 27 & 80 is a base for 81. The key is that 20 x 4 = 80.

Had we'd chosen the right-hand difference of +1/4, it still works, but it's a bit more difficult to do mentally

Awesome

how do you get the base?

all maths and all science has come from india,credit has been taken by greeks,chinese,western civlization,learn about "vedas" to know more.

This is utterly amazing. I've seen different techniques but this one blows the others out of the water!

1.consider to base 40

What about 46x78?

So far I've seen examples with numbers close to each other like " 18x19", "27x28", "34x35".

Thanks for doing math because my son is getting 100 on his test

Sir. How can we multiply 85*15 with this method pls reply....