Curved Surface Area Solution6





In this page curved surface area solution6 we are going to see solution of some practice questions.

Question 11

If the vertical angle and the radius of the right circular cone are 60 degree and 15 cm respectively,then find its height and slant height.

Solution:

Vertical angle of the  right circular cone = 60 degree

                        radius of the cone (r) = 15 cm

In the triangle ABC ∠ABC = 30°

                               BC = 15 cm

Opposite side (BC) = 15 cm

Adjacent side (AB) = ?

Hypotenuse side (AC) = ?

from here we need to find the measurement of the side AC. So we have to use Sinθ.

   Sin θ = Opposite side/Hypotenuse side

   Sin 30° = BC/AC      

    (1/2) = 15/AC

      AC = 30 cm

Slant height (L) = 30 cm


Question 12

If the circumference of the base of the solid right circular cone is 236 and its slant height is 12 cm, find its curved surface area.

Solution:

Circumference of the base = 236 cm

Slant height (L) = 12 cm

              2 Π r = 236

                Π r = 236/2

                 Π r = 118

Curved surface area of cone = Π r l

                                         = 118 (12)

                                         = 1416 cm

Curved surface area of cone = 1416 cm


Question 13

A heap of paddy is in the form of a cone whose diameter is 4.2 m and height is 2.8 m. If the heap is to be covered exactly by a canvas to protect it from rain,then find the area of the canvas needed.

Solution:

Diameter of heap of paddy = 4.2 m

                     r = 4.2/2

                       = 2.1 m

height of paddy (h) = 2.8 m

             L² = r²  + h²

                L = √(2.1)² + (2.8)²

                L = √4.41 + 7.84

                L = √12.25

             L = √ 3.5 x 3.5

             L = 3.5 cm

Curved surface area of heap of paddy = Π r l

                                         = (22/7) x (2.1) x (3.5)

                                         = 22 x (2.1) x (0.5)

                                         = 23.1 cm²

Curved surface area of paddy = 23.1 cm²

curved surface area solution6 curved surface area solution6