Question

Solve: 1001 $\times$ 990 using standard identity.

• A. 999900
• B. 100000
• C. 990000
• D. 119900

Answer 1

The correct option is A

999900

$1010=(1000+10)$
$990=(1000-10)\left(Commutativelaw\right)$
$(1000+10)(1000-10)={1000}^2-{10}^2\left(Identity\right)$
$=1000000-100$
$=999900$