Question

$40\times {5.5}^2-40\times {4.5}^2$ ___

Answer 1

$\Rightarrow 40\times {5.5}^2-40\times {4.5}^2$

$\Rightarrow 40({5.5}^2-{4.5}^2)$

Using $a^2-b^2=(a+b)(a-b)$

$\Rightarrow 40(5.5-4.5)(5.5+4.5)$

$\Rightarrow 40\left(1\right)\left(10\right)$

$\Rightarrow 400$