Question

If each side of a square is doubled, then find the increase percentage of its area.

• A. 200 %
• B. 300 %
• C. 350 %
• D. 400 %

Answer 1

The correct option is B

300 %

Let the side length be x units.

Surface area of solid cubes = 6 x ${}^2$ sq. units

Now, side length becomes 2x units

Surface area of solid cubes = 6 (2x)${}^2$

New surface area of solid cubes = 24 $x^2$ sq. units.

Now, increase in the surface areas = (24$x^2$ - 6$x^2$) sq. units

= 18$x^2$ sq. units.

% increase in surface areas = $\frac{18x^2}{6x^2}$ $\times$ 100%

= 300 %.