In this page curved surface area solution7 we are going to see solution of some practice questions.
The central angle and radius of a sector of a circular disc are 180 degree and 21 cm respectively. If the edges of the sector are joined together to make a hollow cone,then find the radius of the cone.
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) x 2Π R
Here R represents radius of the sector
= (180/360) x 2 x (22/7)x (21)
= (1/2) x 2 x 22x 3
= 66 cm
So,circumference of the base of the cone = 66
2 Π r = 66
2 x (22/7) x r = 66
r = 66 x (1/2) x (7/22)
r = 10.5 cm
Radius and slant height of a solid right circular cone are in the ratio 3:5. If the curved surface area is 60 Π cm², then find its total surface area.
Radius and slant height of a solid right circular cone are in the ratio 3:5.
r : L = 3 : 5
r = 3L/5
Curved surface area of cone = 60 Π cm²
Π r L = 60 Π
Π x (3L/5) x L = 60 Π
L² = 60 Π x (1/Π) x (5/3)
L² = 60 x (5/3)
L² = 100
L = 10
r = 3(10)/5
r = 6
Total surface area = Π r (L + r)
= Π (6) (10 + 6)
= 96 Π cm²
Total surface area of cone = 96 Π cm²
curved surface area solution7 curved surface area solution7