The volume of a right circular cone is `9702 cm^(3)` andheightis 21 cm. Find its curved surface area.

Explanation

Here, h = 21 cm
and volume `= 9702 cm^(3)`
`therefore (1)/(3)pi r^(2)h=9702`
`rArr (1)/(3)xx(22)/(7)xx r^(2)xx21=9702`
`rArr r^(2)=441=21^(2)`
`rArr r = 21 cm`
Now, `l^(2)=h^(2)+r^(2)=21^(2)+21^(2)`
= 441 + 441
= 882
`rArr l=sqrt(882)=21sqrt(2)cm`
`therefore` Curved surface area `= pi r l`
`=(22)/(7)xx21xx21sqrt(2)=1386sqrt(2) cm^(2)`