Example 6: A corn cob (see Fig. 13.17), shaped somewhat like a cone, has the radius of its broadest end as 2.1 cm and length (height) as 20 cm. If each 1 cm2 of the surface of the cob carries an average of four grains, find how many grains you would find on the entire cob.
Cone
Cone is an interesting geometric figure to understand and work upon. You come across so many items in daily life that are conical in shape – like a picnic tent, an ice cream cone, a birthday cap and there are many more that you can think about.
In this chapter we will work on only right circular cones. To understand what a right circular cone is, watch the following video.
Lateral or curved surface area of cone = πrl
r = base radius, l = slant height
Total surface area of cylinder = πrl + πr² = πr (l + r)
r = base radius, l = slant height
To understand the above mentioned formulas, watch the following video. It is highly recommended to watch it before you attempt any cone related questions.
What is Area / Surface area / Volume
It is recommended to understand the core concept of area, surface area and volume before we attempt any question based on these concepts.
Chapter 13 – Surface areas and Volumes
Concepts
- Area / Surface area / Volume – Introduction
- Surface Area of Cube and Cuboid
- Volume Of Cuboid and Cube
- Surface Area of Right Circular Cylinder
- Volume and capacity of Cylinder
- Right circular Cone
- Surface Area of Right circular Cone
- Volume of Cylinder vs Cone
- Litres and Cubic centimetre (cm³)
- Cubic meters to litres
