Last updated at May 29, 2018 by Teachoo

Transcript

Ex13.6 ,7 A lead pencil consists of a cylinder of wood with a solid cylinder of graphite filled in the interior. The diameter of the pencil is 7 mm and the diameter of the graphite is 1 mm. If the length of the pencil is 14 cm, find the volume of the wood and that of the graphite. Volume of graphite Graphite is in shape of cylinder with Radius of graphite = r = (๐ท๐๐๐๐๐ก๐๐ ๐๐ ๐๐๐๐โ๐๐ก๐)/2 = 1/2 ๐๐ = 1/2 ร 1/10 cm = 1/20 cm Height of graphite = h = 14 cm Volume of the graphite cylinder = ฯr2h = (22/7ร1/20ร1/20ร140) mm3 = (22ร1/1ร1/20ร20) mm3 = 0.11 cm3 Volume of wood Volume of wood = Volume of pencil โ Volume of graphite Calculating Volume of the pencil Radius of pencil = r = (๐ท๐๐๐๐๐ก๐๐ ๐๐ ๐๐๐๐๐๐)/2 = 7/2 ๐๐ = 7/2 ร 1/10 cm = 7/20 cm Height of pencil = h = 14 cm Volume of the pencil = ฯr2h = (22/7ร7/20ร7/20ร140) mm3 = 5.39 cm3 Volume of wood = Volume of pencil โ Volume of graphite = 5.39 โ 0.11 cm3 = 5. 28 cm3

Example 2
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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

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 You are here

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.