Question

The slant height of a cone is increased by 10%. If the radius remains the same, the curved surface area is increased by

(a) 10%

(b) 12.1%

(c) 20%

(d) 21%

Answer 1

The formula of the curved surface area of a cone with base radius ‘r’ and slant height ‘l’ is given as

Curved Surface Area = πrl

Now, it is said that the slant height has increased by 10%.So the new slant height is ‘1.1l’

So, now

New Curved Surface Area = 1.1πrl

We see that the percentage increase of the Curved Surface Area is 10%

Hence the correct option is (a).