If the radius of a sphere is tripled, then its surface area increased by

Surface area of sphere with radius r is given by,

Surface area = 4πr2 sq. units

When the radius of the sphere triples, the new radius becomes r1 = 3r

∴ new surface area of sphere = 4π × (3r)2 = 36πr2 sq. units

$(\therefore \;\% \;increase\;in\;area\; = \frac{{new\;area - original\;area}}{{original\;area}} \times 100)$

$(\Rightarrow \% \;increase\;in\;area\; = \frac{{36\;\pi {r^2} - 4\;\pi {r^2}}}{{4\;\pi {r^2}}} \times 100 = 800)$

∴ Surface area of a sphere increases by 800% when its radius triples.