If each side of a cube is reduced by 50%, the surface area will reduced by.
Answer & explanation
Correct answer: option 1
The correct answer is Option 1: 75%
Let the original side of the cube = a
1. Original surface area
$S_1 = 6a^2$
2. New side after 50% reduction
$a - 50\% \text{ of } a = \frac{a}{2}$
3. New surface area
$S_2 = 6\left(\frac{a}{2}\right)^2 = 6 \times \frac{a^2}{4} = \frac{6a^2}{4} = \frac{3}{2}a^2$
4. Reduction in surface area
$6a^2 - \frac{3}{2}a^2 = \frac{12a^2 - 3a^2}{2} = \frac{9a^2}{2}$
5. Percentage reduction
$\frac{\frac{9a^2}{2}}{6a^2} \times 100 = \frac{9}{12} \times 100 = 75\%$