NCERT Solutions
Class 9 - Mathematics - Chapter 11: SURFACE AREAS AND VOLUMES
EXERCISE 11.4

Question. 1

Find the volume of a sphere whose radius is:

(i) 7 cm    (ii) 0.63 m

Answer:

(i) 1437 1/3 cm³    (ii) 1.05 m³ (approx.)

Question. 2

Find the amount of water displaced by a solid spherical ball of diameter:

(i) 28 cm    (ii) 0.21 m

Answer:

(i) 11498 2/3 cm³    (ii) 0.004851 m³

Question. 3

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?

Answer:

345.39 g (approx.)

Question. 4

The diameter of the moon is approximately one-fourth of the diameter of the earth. What fraction of the volume of the earth is the volume of the moon?

Answer:

1/64

Question. 5

How many litres of milk can a hemispherical bowl of diameter 10.5 cm hold?

Answer:

0.303 l (approx.)

Question. 6

A hemispherical tank is made up of an iron sheet 1 cm thick. If the inner radius is 1 m, find the volume of the iron used to make the tank.

Answer:

0.06348 m³ (approx.)

Question. 7

Find the volume of a sphere whose surface area is 154 cm².

Answer:

179 2/3 cm³

Question. 8

A dome of a building is in the form of a hemisphere. From inside, it was white-washed at the cost of ₹4989.60. If the cost of white-washing is ₹20 per square metre, find the:

(i) inside surface area of the dome

(ii) volume of the air inside the dome

Answer:

(i) 249.48 m²    (ii) 523.9 m³ (approx.)

Question. 9

Twenty-seven solid iron spheres, each of radius r and surface area S, are melted to form a sphere with surface area S'. Find the:

(i) radius r' of the new sphere

(ii) ratio of S and S'

Answer:

(i) 3r    (ii) 1 : 9

Question. 10

A capsule of medicine is in the shape of a sphere of diameter 3.5 mm. How much medicine (in mm³) is needed to fill this capsule?

Answer:

22.46 mm³ (approx.)

NCERT Solutions Class 9 – Mathematics – Chapter 11: SURFACE AREAS AND VOLUMES – EXERCISE 11.4 | Detailed Answers