Question

$78\times 82$

• A. $6396$
• B. $6390$
• C. $6391$
• D. $6394$

Answer 1

The correct option is A $6396$

$\left(78\right)\left(82\right)$
$=(80-2)(80+2)$
Using ,
$(a-b)(a+b)=a^2-b^2$ we get,
$(80{)}^2-(2{)}^2$
$=6400-4$
$=6396$