Surface Areas & Volumes | Exercise 13.2 | Q10

Question 10: In the adjacent figure, you see the frame of a lampshade. It is to be covered with a decortive cloth. The frame has a base diameter of 20 cm and height of 30 cm. A margin of 2.5 cm is to be given for folding it over the top and bottom of the frame. Find how much cloth is required for covering the lampshade.

Video Explanation

Explanatory Answer | Exercise 13.2 Question 10

The curved surface of the cylindrical lampshade is to be covered by the decorative cloth.
So, the area covered by decorative cloth = curved surface area of the cylinder.

The total cloth required will include a margin of 2.5 cm at the top and the bottom.
i.e., the height of the cylinder has to be increased by 5 cm to accommodate this margin.

Curved surface area of cylinder = 2πrh
Take π = \\frac{22}{7})

Base diameter = 20 cm. So, base radius = 10 cm.
Height of the lampshade = 30 cm.
Add 2.5 cm margin at the top and bottom, height of cloth required = 30 + 2.5 + 2.5 = 35 cm

Area of decorative cloth required = 2 × \\frac{22}{7}) × 10 × 35
= 2200 cm²

Exercise 13.1 | Surface Area of Cubes & Cuboids

1. Class 9 Exercise 13.1 Question 3 | Height of hall ▶
2. Class 9 Exercise 13.1 Question 6 | TSA of Herbarium ▶
3. Class 9 Exercise 13.1 Question 7 | Shanti Sweets ▶

Exercise 13.2 | Surface Area of Cylinders

1. Class 9 Exercise 13.2 Question 3 | CSA TSA of Metal Pipe ▶
2. Class 9 Exercise 13.2 Question 4 | Roller & Playground ▶
3. Class 9 Exercise 13.2 Question 9 | Cylindrical Petrol Tank ▶
4. Class 9 Exercise 13.2 Question 10 | CSA of Decorative Lampshade ▶

Exercise 13.3 | Surface Area of Cones

1. Class 9 Exercise 13.3 Question 5 | Length of Tarpaulin 3 m wide ▶
2. Class 9 Exercise 13.3 Question 8 | Cost of painting conical barricades ▶

Exercise 13.4 | Surface Area of Spheres & Hemispheres

1. Class 9 Exercise 13.4 Question 8 | Outer CSA of hemispherical bowl ▶
2. Class 9 Exercise 13.4 Question 9 | Surface area of sphere & Cylinder ▶