Last updated at May 29, 2018 by Teachoo

Transcript

Ex 13.2, 9 Find The lateral or curved surface area of a closed cylindrical petrol storage tank that is 4.2 m in diameter and 4.5 m high. [๐ด๐ ๐ ๐ข๐๐ ๐= 22/7] Height (h) of cylindrical tank = 4.5 m Radius (r) of the circular end of cylindrical tank = (4.2/2) m = 2.1 m Curved Surface Area of tank = 2ฯrh = (2ร22/7ร2.1ร4.5) m2 = (2ร22/7ร21/10ร45/10) m2 = (2ร22ร3/10ร45/10) m2 = 59.4 m2 Ex 13.2, 9 Find (ii) How much steel was actually used, if 1/12 of the steel actually used was wasted in making the tank. [๐ด๐ ๐ ๐ข๐๐ ๐= 22/7] h = 4.5 m , r = 2.1 m Total surface area of tank = (2ฯr (r + h)) = 2ร22/7ร2.1ร(2.1+ 4.5) = 2ร22/7ร2.1ร(6.6) = 2ร22/7ร21/10ร66/10 = 87.12 m2 Let Amount of steel used in making the tank = x Steel wasted = ๐ฅ/12 Given that Amount of steel required โ Amount of steel wasted = TSA of tank x โ ๐ฅ/12 = 87.12 11/12 ๐ฅ = 87.12 x = 12/11 ร 87.12 x = 95.04 m2 Therefore, 95.04 m2 steel was used in actual while making such a tank.

Chapter 13 Class 9 Surface Areas and Volumes

Example 2
Important

Ex 13.1, 6 Important

Ex 13.1, 7 Important

Ex 13.2, 3 Important

Ex 13.2, 4 Important

Ex 13.2, 9 Important You are here

Example 6 Important

Ex 13.3, 3 Important

Ex 13.3, 5 Important

Ex 13.4, 3 Important

Ex 13.4, 8 Important

Ex 13.4, 9 Important

Ex 13.5, 6 Important

Ex 13.5, 8 Important

Ex 13.5, 9 Important

Example 14 Important

Ex 13.6, 3 Important

Ex 13.6, 7 Important

Ex 13.7, 5 Important

Ex 13.7, 6 Important

Ex 13.7, 7 Important

Ex 13.7, 8 Important

Example 18 Important

Ex 13.8, 4 Important

Surface Area and Volume Formulas Important

Class 9

Important Questions for Exam - Class 9

- Chapter 1 Class 9 Number Systems
- Chapter 2 Class 9 Polynomials
- Chapter 3 Class 9 Coordinate Geometry
- Chapter 4 Class 9 Linear Equations in Two Variables
- Chapter 5 Class 9 Introduction to Euclid's Geometry
- Chapter 6 Class 9 Lines and Angles
- Chapter 7 Class 9 Triangles
- Chapter 8 Class 9 Quadrilaterals
- Chapter 9 Class 9 Areas of parallelograms and Triangles
- Chapter 10 Class 9 Circles
- Chapter 11 Class 9 Constructions
- Chapter 12 Class 9 Herons Formula
- Chapter 13 Class 9 Surface Areas and Volumes
- Chapter 14 Class 9 Statistics
- Chapter 15 Class 9 Probability

About the Author

Davneet Singh

Davneet Singh is a graduate from Indian Institute of Technology, Kanpur. He has been teaching from the past 8 years. He provides courses for Maths and Science at Teachoo. You can check his NCERT Solutions from Class 6 to 12.