Question

The base radius of a cone made by rolling up a sector is 3cm and its slant height is 15cm
(i) what is the radius of the sector
(ii) what is the central angle of the sector
(iii) find the area

Answer 1

Answer:

240

o

is

360

240

=

3

2

part of the central angle of the big circle.

So the radius of the cone is

3

2

part of the radius of the big circle,

which is 15×

3

2

=10cm

When cone is made using the sector, its slant height = 15 cm

⇒ Height of the cone =

15

2

−10

2

=

225−100

=

125

=5

5

cm

Now, volume of the cone =

3

1

π

2

h=

3

1

×π×10×10×5

5

=

3

500

5

πcm

3