Question

Find $249\times 251$ without actual multiplication.

Answer 1

$249\times 251$
$(250-1)(250+1)$
It is in the form of $(a-b)(a+b)$
$\Rightarrow (250{)}^2-(1{)}^2$
$\Rightarrow 62500-1$
$\Rightarrow 62499$
$62499$ is the product of $249\times 251$.