Mathematics for IGCSE & O level - Mensuration (Section 9 - No. 2)
If the radius of a sphere is doubled, how does its surface area change?
It doubles.
It triples.
It quadruples.
It is halved.
Giải thích
The surface area of the sphere = 4πr². If r is doubled, the surface area becomes 4π(2r)² = 16πr².