Question:If the surface area of two sphere are in the ratio of`4 : 25`then the ratio of their volumes is :
A `4 : 25`
B `25 : 4`
C `125 :8`
D `8 : 125`
/113
+ Answer
D
+ ExplanationLet their radii be R and r. Then,
`(πR^2)/(4πr^2)`
`= 4/25 ⇒ (R/r)^2`
`= (2/5)^2 or R/r`
`2/5.`
:. Ratio of their volumes
`= (4/3 πR^3)/(4/3 πr^3)`
`= (R/r)^3`
`= (2/5)^3`
`= 8/125`