NCERT Solutions for Class 9 Maths Chapter 13 Exercise 13.9 Optional exercise of surface areas and volumes in English Medium and Hindi Medium free to use online. NCERT Solutions for class 9 all subjects based on Latest CBSE Syllabus are available free to download. The solutions of other exercises like Exercise 13.1 & 13.2 or Exercise 13.3 & 13.4 or Exercise 13.5 & 13.6 or Exercise 13.7 & 13.8 are also given to use online.

## NCERT Solutions for Class 9 Maths Chapter 13 Exercise 13.9 Optional

If you need solutions in Hindi, Click for Hindi Medium solutions of 9 Maths Exercise 13.9

### 9 Maths Chapter 13 Exercise 13.9 in Hindi

To get the solutions in English, Click for English Medium solutions.

##### Class 9 Maths Chapter 13 Optional Exercise

###### Practice Questions for Exams

- A right triangle having sides 6 cm, 8 cm and 10 cm is revolved about the side of length 8 cm. Find the volume of the solid so formed. [Answer: 288π cm³]
- A right circular cone is 5.4 cm high and radius of its base is 2 cm. It is melted and recast into another right circular cone with radius of base as 1.5 cm. Find the height of new cone formed. [Answer: 9.6 cm]
- A cylindrical tub of radius 12 cm contains water to the depth of 20cm. A spherical ball is dropped into the tub raising the level of water by 6.75 cm. What is the radius of ball? [Answer: 9 cm]
- A cylinder is within the cube touching all the vertical faces. A cone is inside the cylinder. If their height are the same with the same base. Find the ratio of their volumes. [Answer: V1:V2:V3 = 42:33:11]
- A plot of land is in the form of rectangle has dimension 240 m x 180 m. A drain let 10 m wide is dug around it (on the outside) and the earth dug out is evenly spread out over the plot increasing its surface level by 25 cm. Find the depth of the drain let. [Answer: 1.227 m]
- A residential colony has a population of 5400 and 60 litres of water is required per person per day. For the effective utilization of rain water, a group of people decided to the WATER HARVESTING. They constructed a water reservoir measuring 48 m x 27 m x 25 m to collect the rain water. a) For how many days the water of this tank is sufficient if during rain the height of water level is 5 m. b) Which value is shown by the group of people? [Answer: 20 days, Environmental Values, Cooperation]
- 50 students of class IX planned a visit to an old age home and to spend the whole day with its inmates. Each one prepared a cylindrical flower vase using card board to gift the inmates. The radius of cylinder is 4.2 cm and the height is 11.2 cm. a) What is the amount spent for purchasing the card board at the rate of ₹ 20 per 100 m². b) What values are depicted by the students? [Answer: ₹ 3511.20]
- Rahul wanted to make a temporary shelter for street dogs, by making a box like structure with tarpaulin that covers all the four sides and the top of the house. How much tarpaulin would be required to make the shelter of height 2.5 m with base dimensions 4 m x 3 m. Assuming stitching margin is negligible. Which values are depicted in this question? [Answer: 47 m², Care for animals]