Question

Side of a cube is increased by $50$%, then what percent increase will be in the area of the vertical faces of the cube?

• A. $125$%
• B. $150$%
• C. $100$%
• D. $50$%

Answer 1

Answer: (A)

$125$%

Let the side be $a$
new side $=1.5a$
Area of $4$ walls (old) $=4a^2$
Area of $4$ walls (new) $=4\times 2.25a^2=9a^2$
$\therefore$ % increase $=\frac{5a^2}{4a^2}\times 100=\frac{5}{4}\times 100$
% increase $=125$%.

Hence, option A is correct.