Question

without actual multiplication find the value of : 1001 × 999.
pls answer correct and fast.
I'll mark u the brainliest ​

Answer 1

Both those numbers are 1 on either side of 1000. The answer is to square 1000 and subtract 1 and I'll show you why.

First try in your head with some smaller numbers. 10 x 10, then 9 x 11, then 8 x 12. Noticing a pattern? When you multiple 2 numbers together that are plus and minus the same amount from another number (8 and 12 are both 2 from 10 etc) you can obtain the answer by squaring the middle number and subtracting the square of the distance from the first numbers. Eg 8 x 12 = 10^2 - 2^2

It may look like magic but expand (n-a)(n+a) and see what you get.

So 1001 × 999 = 1000^2 - 1^2 = 1000000 - 1 = 999999