Question

A right circular cylinder just encloses a sphere of radius r. Find 

i) surface area of the sphere 

ii) curved surface area of the cylinder 

iii) ratio of the areas obtained in (i) and (ii)

Answer 1

i) Radius of the sphere = radius of the cylinder = r 

∴Surface area of the sphere = 4πr² 

ii) C.S.A. of cylinder = 2πr (2r) [∵ h = 2r]

= 4πr² 

iii) Ratio of (i) and (ii) = 4πr² : 4πr² = 1:1