= 4/3 × 22/7 × 2.1 × 2.1 × 2.1 =38.808cm³
Example-7.

Find the volume and the total surface area of a hemisphere of radius 3.5 cm.[]

Radius of sphere (r) is 3.5 cm = 7/2 cm

Volume of hemisphere = 2/3

2/3 × 22/7 × 7/2 × 7/2 × 7/2 = 539/6 = 89.83 cm ³

Total surface area = 3 πr²

3 × 22/7 × 7/2 × 7/2 = 231/2 = 115.5 cm²

1. A joker’s cap is in the form of right circular cone whose base radius is 7cm and height is 24 cm. Find the area of the sheet required to make 10 such caps.


2. A sports company was ordered to prepare 100 paper cylinders for packing shuttle cocks. The required dimensions of the cylinder are 35 cm length /height and its radius is 7 cm. Find the required area of thick paper sheet needed to make 100 cylinders?


3. Find the volume of right circular cone with radius 6 cm. and height 7cm.


4. The lateral surface area of a cylinder is equal to the curved surface area of a cone. If their bases are the same, find the ratio of the height of the cylinder to the slant height of the cone.


5. A self help group wants to manufacture joker’s caps of 3cm. radius and 4 cm. height. If the available paper sheet is 1000 cm2, then how many caps can be manufactured from that paper sheet?


6. A cylinder and cone have bases of equal radii and are of equal heights. Show that their volumes are in the ratio of 3:1.


7. The shape of solid iron rod is cylinderical. Its height is 11 cm. and base diameter is 7cm.Then find the total volume of 50 such rods.