# The diameter of a metallic ball is 4.2 cm. What is the mass of the ball, if the density of the metal is 8.9 g per cm^{3}?

**Solution:**

The diameter of the metallic ball = 4.2 cm

The density of the metal = 8.9 g per cm^{3}.

We know that,

Density = Mass / Volume

Volume of a sphere = 4/3πr^{3}

Diameter of the metallic ball, d = 4.2cm

Radius of the metallic ball, r = 4.2/2cm = 2.1cm

The volume of the metallic ball = 4/3πr^{3}

= 4/3 × 22/7 × 2.1cm × 2.1cm × 2.1cm

= 38.808 cm³

Now, Mass = Volume × Density

Mass of the metallic ball = 38.808 cm^{3} × 8.9g / cm³

= 345.3912 g

= 345.39 g (approx.)

Thus, the mass of the ball is 345.39 g.

**Video Solution:**

## The diameter of a metallic ball is 4.2 cm. What is the mass of the ball, if the density of the metal is 8.9 g per cm³?

### NCERT Solutions for Class 9 Maths - Chapter 13 Exercise 13.8 Question 3:

**Summary:**

It is given that the diameter of a metallic ball is 4.2 cm. If the density of the metal is 8.9 g per cm³, we have found that the mass of the ball is 345.39 g.