Last updated at Feb. 25, 2017 by Teachoo

Transcript

Example 3 A wooden toy rocket is in the shape of a cone mounted on a cylinder, as shown in figure. The height of the entire rocket is 26 cm, while the height of the conical part is 6 cm. The base of the conical portion has a diameter of 5 cm, while the base diameter of the cylindrical portion is 3 cm. If the conical portion is to be painted orange and the cylindrical portion yellow, find the area of the rocket painted with each of these colours. (Take π= 3.14) Area to be painted orange = Curved surface area of the cone + Base area of the cone – Base area of the cylinder Area to be painted yellow = Curved Surface Area of the cylinder + Area of one bottom base of the cylinder Curved surface area of the cone Curved Surface area of cone = 𝜋𝑟𝑙 Diameter of conical portion = 5 cm Radius of conical portion = r = 𝐷𝑖𝑎𝑚𝑒𝑡𝑒𝑟/2 = 5/2 = 2.5 cm Height of the conical part = h = 6 cm We need to find 𝑙 first We know that l2 = h2 + r2 l2 = (6)2 + (5/2)^2 l2 = 36 + 25/4 l2 = (36(4) + 25)/4 l2 = 169/4 l = √(169/4) l = √(〖13〗^2/2^2 ) l = 13/2 l = 6.5 cm Curved Surface area of cone = 𝜋𝑟𝑙 = 3.14 ×2.5×6.5 = 51.025 cm2 Base area of the cone Base of cone is a circle with radius = radius of cone = 2.5cm Base area of cone = Area of circle = 𝜋𝑟2 = 3.14 × (2.5)2 = 3.14×6.25 = 19.625 cm2 Curved Surface area of the cylinder Diameter of cylinder = 3 Radius of cylinder = r = 𝐷𝑖𝑎𝑚𝑒𝑡𝑒𝑟/2 = 3/2 = 1.5 cm Height of cylinder = Total height – Height of cone = 26 – 6 = 20 cm Curved Surface area of the cylinder = 2𝜋𝑟h = 2 ×3.14×1.5×20 = 188.4 cm2 Base area of the cylinder Base of cone is a circle with radius = radius of cylinder = 1.5 cm Base area of cylinder = Area of circle = 𝜋𝑟2 = 3.14 × (1.5)2 = 7.065 cm2 Hence, Area to be painted orange = Curved surface area of the cone + Base area of the cone – Base area of the cylinder = 51.025 + 19.625 – 7.0625 = 70.65 – 7.0625 = 63.58 cm2 Area to be painted yellow = Curved Surface Area of the cylinder + Area of one bottom base of the cylinder = 188.4 + 7.065 = 195.465 cm2 Hence, area to be painted yellow = 195.465 cm2

Chapter 13 Class 10 Surface Areas and Volumes

Example 2
Important

Example 3 Important You are here

Ex 13.1, 4 Important

Ex 13.1, 9 Important

Example 6 Important

Example 7 Important

Example 9 Important

Example 11 Important

Ex 13.3, 8 Important

Ex 13.3, 9 Important

Example 12 Important

Ex 13.4, 4 Important

Ex 13.4, 5 Important

Surface Area and Volume Formulas Important

Class 10

Important Questions for Exam - Class 10

- Chapter 1 Class 10 Real Numbers
- Chapter 2 Class 10 Polynomials
- Chapter 3 Class 10 Pair of Linear Equations in Two Variables
- Chapter 4 Class 10 Quadratic Equations
- Chapter 5 Class 10 Arithmetic Progressions
- Chapter 6 Class 10 Triangles
- Chapter 7 Class 10 Coordinate Geometry
- Chapter 8 Class 10 Introduction to Trignometry
- Chapter 9 Class 10 Some Applications of Trignometry
- Chapter 10 Class 10 Circles
- Chapter 11 Class 10 Constructions
- Chapter 12 Class 10 Areas related to Circles
- Chapter 13 Class 10 Surface Areas and Volumes
- Chapter 14 Class 10 Statistics
- Chapter 15 Class 10 Probability

About the Author

Davneet Singh

Davneet Singh is a graduate from Indian Institute of Technology, Kanpur. He has been teaching from the past 9 years. He provides courses for Maths and Science at Teachoo.