Question

if the radius of a sphere is doubled what will happen to its surface area ?

Answer 1

let the original radius be R

So the new radius is 2R


Original SA = 4πr²
Original SA = 4 π × R² ........ (i)

New SA = 4π × (2R)²
New SA= 4π×4R²
New SA= 16 πR²
New SA= 4(4 πR²). .....(ii)

from (ii) and (i)
new SA = 4 Original SA

so when radius is doubled, SA is four times