Curved Surface Area Solution2

In this page curved surface area solution2 we are going to see solution of some practice questions.

Question 4

A mansion has 12 right cylindrical pillars each having radius 50 cm and height 3.5 m. Find the cost to paint the lateral surface of pillars at \$ 20 per square meter.

Solution:

The pillars of the mansion are in the shape of cylinder

Curved surface area of one pillar = 2 Π r h

= 0.5 m

height = 3.5 m

Curved surface area of one pillar = 2 x (22/7) x 0.5 x 3.5

= 2 x 22 x 0.5 x 0.5

= 11 m²

Curved surface of 12 pillars = 12 x 11

= 132 m²

Cost to paint per m² = \$ 20

Total cost = 20 x 132

= \$ 2640

Required cost of painting 132 m² is \$ 2640

Question 5

The total surface area of a solid right circular cylinder are 231 cm². Its curved surface area is two thirds of the total surface area. Find the radius and height of the cylinder.

Solution:

Curved surface area = (2/3) x Total surface area

2 Π r h  = (2/3) x 231

2 Π r h  = 2 x 77

2 Π r h  = 154

Total surface area of the cylinder = 231 cm²

2 Π r (h + r) = 231

2 Π r h + 2 Π r²  = 231

154 + 2 Π r²  = 231

2 Π r²  = 231 - 154

2 Π r²  = 77

2 x (22/7) x r²  = 77

r²  = 77 x (7/22) x (1/2)

r²  = (7/2) x (7/2)

r = (7/2) cm

2 Π r h  = 154

x (22/7) x (7/2) x= 154

h = 154 x (1/2)  x (7/22) x (2/7)

h = 7 cm 