"Question 7 A closed cylindrical tank of radius 7 m and height 3 m is made from a sheet of metal. How much sheet of metal is required?
Class 8 Mensuration Page 186"
Answers
Mensuration:
Mensuration is the branch of mathematics which concerns itself with the measurement of Lengths, areas & volume of different geometrical shapes or figures.
Surface area:
The surface area of a solid is the sum of the areas of the plane or curved faces of the solid.
It is measured in square units such as square centimetre (cm²) and square metre (m²).
Cylinder:
Whenever we talk about a total surface area of a cylinder the cylinder must be closed at both the ends by two circular regions or it should be a cylindrical solid object.
Total surface area of a solid cylinder= curved surface area + sum of the areas of two circular ends of the cylinder
= 2πrh+ 2πr²
Total surface area of a solid cylinder= 2πr(h+r)
The lateral surface area of the curved surface area of a cylinder= 2πrh
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Solution:
Given:
Radius of Cylindrical tank(r)= 7m
Height of cylindrical tank (h)=3m
Total surface area of cylindrical tank= 2πr(h+r)
Total surface area of cylindrical tank=2× (22/7)×7(3+7)
= 44×10= 440 m²
Total surface area of cylindrical tank= 440 m²
Hence, 440 m² sheet is required .
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Hope this will help you....
FORMULES :
1. CSA OF CYLINDER = 2 X pie X r X h
2.TSA OF CYLINDER = 2 X pie x r (r + h)
3. VOLUME OF CYLINDER = pie X r square X h
I think this help you