Question

If each side of a cube is doubled, its surface area
(a) is doubled
(b) becomes $4$ times
(c) becomes $6$ times
(d) becomes $8$ times

Answer 1

(b) becomes $4$ times.
Let the side of the cube be $a$ units.
Surface area $=6a^2$ sq. units
Now, new side$=2a$ units.
New surface area $=6(2a{)}^2$sq units
$=6\times 4\times a^2$
$=4\left(6a^2\right)$ sq. units, where $6a^2$ is the surface area of the original cube.
Thus, the new surface area becomes $4$ times the original area.