# In Fig. 13.12, you see the frame of a lampshade. It is to be covered with a decorative 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.

**Solution:**

Given: The frame has a base diameter of 20 cm and height of 30 cm.

Since the frame is cylindrical in shape, the cloth required to cover the lampshade will be equal to the curved surface area of cylinder.

The amount of cloth required to cover the cylinder will be equal to the curved surface area of the cylinder.

The curved surface area of a right circular cylinder = 2πrh

Diameter of the frame, d = 20 cm

Radius of the frame, r = d/2 = 20/2 cm = 10 cm

Height of the cylinder frame = 30 cm

Here, height will be equal to the height of cylinder plus 2.5 cm margin on both the sides which is used as an extra part for folding.

Height of the lampshade, h = 30 cm + 2.5 cm + 2.5 cm = 35 cm

Thus, cloth required for covering the lampshade = 2πrh

= 2 × 22/7 × 10 cm × 35 cm

= 2200 cm²

Thus, the area of the cloth required is 2200 cm².

**☛ Check: **NCERT Solutions for Class 9 Maths Chapter 13

**Video Solution:**

## In Fig. 13.12, you see the frame of a lampshade. It is to be covered with a decorative 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.

Class 9 Maths NCERT Solutions Chapter 13 Exercise 13.2 Question 10

**Summary:**

It is given that the frame of a lampshade is to be covered with a decorative cloth. The frame has a base diameter of 20 cm and height of 30 cm with a margin of 2.5 cm given for folding it over the top and bottom of the frame.We have found that the area of cloth required to cover the frame is 2200 cm².

**☛ Related Questions:**

- Curved surface area of a right circular cylinder is 4.4 m². If the radius of the base of the cylinder is 0.7 m, find its height.
- The inner diameter of a circular well is 3.5 m. It is 10 m deep. Find i) Its inner curved surface area ii) The cost of plastering this curved surface at the rate of ₹40 per m².
- In a hot water heating system, there is a cylindrical pipe of length 28 m and diameter 5 cm. Find the total radiating surface in the system.
- Find i) The lateral or curved surface area of a closed cylindrical petrol storage tank that is 4.2 m in diameter and 4.5 m high. ii) How much steel was actually used, if 1/12 of the steel actually used was wasted in making the tank?

visual curriculum