14.The central angle and radius of a sector of a circular disc are 180

1.	14.The central angle and radius of a sector of a circular disc are 180Â° and 21 cmrespectively. If the edges of the sector are joined together to make a hollow cone,then find the radius of the cone.
Answer» The cone is being created by joining the radius. So the radius of the sector is going to be the slant height of the cone. Slant height (L) = 21 cm Arc length of the sector = Circumference of the base of the cone Length of arc = (θ/360)x2Π R Here R represents radius of the sector = (180/360)x2x(22/7)x(21) = (1/2)x2x22x3 = 66 cm So,circumference of the base of the cone =66 2 Π r = 66 2x(22/7)xr = 66 r = 66x(1/2)x(7/22) r = 10.5 cm Radius of the cone =10.5 cm

14.The central angle and radius of a sector of a circular disc are 180Â° and 21 cmrespectively. If the edges of the sector are joined together to make a hollow cone,then find the radius of the cone.

Answer»

The cone is being created by joining the radius. So the radius of the sector is going to be the slant height of the cone.

Slant height (L) = 21 cm

Arc length of the sector = Circumference of the base of the cone

Length of arc = (θ/360)x2Π R

Here R represents radius of the sector

= (180/360)x2x(22/7)x(21)

= (1/2)x2x22x3

= 66 cm

So,circumference of the base of the cone =66

2 Π r = 66

2x(22/7)xr = 66

r = 66x(1/2)x(7/22)

r = 10.5 cm

Radius of the cone =10.5 cm