Question

Compute the value of following expression $109\times 91$

• A. $9919$
• B. $9819$
• C. $9991$
• D. $9929$

Answer 1

The correct option is A

$9919$

The given expression is

$109\times 91$

$=(100+9)(100-9)$

$=(100{)}^2-(9{)}^2\left[\right(x-y\left)\right(x+y)=x^2-y^2]$

$=10000-81$

$=9919$