Q149
ArithmeticGeometry & Mensuration
The percentage increase in the surface area of a cube when each side is doubled is
- a.25%
- b.50%
- c.150%
- d.300%
Answer: (D) 300%
Surface area of a cube with side $a$ is $6a^2$. Doubling the side to $2a$ gives a new surface area of $6(2a)^2 = 24a^2$, which is 4 times the original — an increase of $\dfrac{24a^2-6a^2}{6a^2}\times 100\% = 300\%$.