Question

If the base radius and the height of a right circular cone are increased by 20%, then the percentage increase in volume is approximately

(a) 60

(b) 68

(c) 73

(d) 78

Answer 1

The formula of the volume of a cone with base radius ‘r’ and vertical height ‘h’ is given as

Volume of cone =

= V

It is given that the base radius and the height are increased by 20%. So now the base radius is ‘1.2r’ and the height is ‘1.2h’.

So,

The volume of the modified cone =

=

= 1.728 V

Hence the percentage increase in the volume of the cone is 72.8%, which is approximately equal to 73%.

Hence the correct answer is option (c).