Question

Evaluate without actual multiplication.
$101\times 99$

Answer 1

$101\times 99=(100+1)(100-1)$

We know suitable identity is $(x+y)(x-y)=x^2-y^2$

Therefore, the value of $(100+1)(100-1)$ is

$=(100{)}^2-(1{)}^2$

$=10000-1$

$=9999$