NCERT Solutions
Class 9 - Mathematics - Chapter 11: SURFACE AREAS AND VOLUMESEXERCISE 11.4
Class 9 - Mathematics - Chapter 11: SURFACE AREAS AND VOLUMES
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.)