# The inner diameter of a cylindrical wooden pipe is 24 cm and its outer diameter is 28 cm. The length of the pipe is 35 cm. Find the mass of the pipe, if 1 cm^{3} of wood has a mass of 0.6 g.

**Solution:**

Since the cylindrical wooden pipe is made up of two concentric circles at the top and bottom, we will find the volume of both cylinders.

The volume of a cylinder of base radius, r, and height, h = πr^{2}h

The volume of wood can be obtained by finding the difference between the volumes of both the outer and inner cylinders.

Outer diameter of the pipe = 28 cm

Outer radius of the pipe, R = 28/2 = 14 cm

Inner diameter of the pipe = 24 cm

Inner radius of the pipe, r = 24/2 = 12cm

Length of the pipe, h = 35 cm

Volume of the outer cylinder, V_{1} = π R^{2 }h

V_{1} = 22/7 × 14cm × 14cm × 35cm

= 21560 cm^{3}

Volume of the inner cylinder, V_{2} = πr^{2}h

V_{2} = 22/7 × 12cm × 12cm × 35cm

= 15840 cm^{3}

The volume of the wood used = Volume of the outer cylinder – Volume of the inner cylinder

= 21560 cm^{3} - 15840 cm^{3}

= 5720 cm^{3}

Mass of 1 cm^{3} wood is 0.6 g

Mass of 5720 cm^{3} wood = 5720 × 0.6g

= 3432 g

= (3432/1000) kg

= 3.432 kg

Thus, the mass of the wooden pipe is 3.432 kg

**Video Solution:**

## The inner diameter of a cylindrical wooden pipe is 24 cm and its outer diameter is 28 cm. The length of the pipe is 35 cm. Find the mass of the pipe, if 1 cm³ of wood has a mass of 0.6 g.

### NCERT Solutions for Class 9 Maths - Chapter 13 Exercise 13.6 Question 2:

**Summary:**

It is given that the inner diameter of a cylindrical wooden pipe is 24 cm and its outer diameter is 28 cm. If the length of the pipe is 35 cm, and 1 cm³ of wood has a mass of 0.6 g, the total mass of the wooden pipe is 3.432 kg.