Question

Side of square is increased by $10\%$ find the percent increase in its area?

Answer 1

Let the side of square be x
Area = $x^2$
New length = 1 + 0.1x =1.1x
New area = 1.1x $\times$ 1.1x = 1.21 $x^2$
$\%$ age change in area = $=\frac{(1.21x^2-x^2)}{x^2\times 100}=21\%$