Question

the radius and slant height of a cone are in the ratio of 3:5. if its total surface area is 2112/7 sq.cm, find the slant height.​

Answer 1

Answer:

We have,

r:l=3:5

l

r

=

5

3

r=

5

3l

........(1)

Curved surface area =60π cm

2

We know that the curved surface area of the cone

=πrl

So,

πrl=60π

rl=60

5

3l

2

=60 From equation (1)

l

2

=100

l=10 cm

So, r=6 cm

We know that the total surface area

=πr(r+l)

So,

=

7

22

×6(6+10)

=

7

22

×6×16

=

7

2112

=301

7

5

cm

2

Hence, this is the answer