NCERT Solutions
Class 9 - Mathematics - Chapter 11: SURFACE AREAS AND VOLUMES
EXERCISE 11.3

Question. 1

Find the volume of the right circular cone with:

(i) radius 6 cm, height 7 cm

(ii) radius 3.5 cm, height 12 cm

Answer:

(i) 264 cm³    (ii) 154 cm³

Question. 2

Find the capacity in litres of a conical vessel with:

(i) radius 7 cm, slant height 25 cm

(ii) height 12 cm, slant height 13 cm

Answer:

(i) 1.232 l    (ii) 11/35 l

Question. 3

The height of a cone is 15 cm. If its volume is 1570 cm³, find the radius of the base.

Answer:

10 cm

Question. 4

If the volume of a right circular cone of height 9 cm is 48π cm³, find the diameter of its base.

Answer:

8 cm

Question. 5

A conical pit of top diameter 3.5 m is 12 m deep. What is its capacity in kilolitres?

Answer:

38.5 kl

Question. 6

The volume of a right circular cone is 9856 cm³. If the diameter of the base is 28 cm, find:

(i) height of the cone

(ii) slant height of the cone

(iii) curved surface area of the cone

Answer:

(i) 48 cm    (ii) 50 cm    (iii) 2200 cm²

Question. 7

A right triangle ABC with sides 5 cm, 12 cm and 13 cm is revolved about side 12 cm. Find the volume of the solid so obtained.

Answer:

100π cm³

Question. 8

If the triangle ABC in Question 7 above is revolved about the side 5 cm, then find the volume of the solid so obtained. Find also the ratio of the volumes of the two solids obtained in Questions 7 and 8.

Answer:

240π cm³; 5 : 12

Question. 9

A heap of wheat is in the form of a cone whose diameter is 10.5 m and height is 3 m. Find its volume. The heap is to be covered by canvas to protect it from rain. Find the area of the canvas required.

Answer:

86.625π m³, 99.825 m²

NCERT Solutions Class 9 – Mathematics – Chapter 11: SURFACE AREAS AND VOLUMES – EXERCISE 11.3 | Detailed Answers