9. • No edges or
vertices.
• The entire
curved surface is
considered as one
surface.
10. Let’s compare a sphere with radius ‘r’ with a
cylinder of the same radius.
11. Now when we insert the sphere into the cylinder, we can see
that the height of cylinder = diameter of the sphere
i.e h = d = 2 r
12. Then proof of this was given to us by the famous
mathematician Archimedes and it says that ,
Surface Area of sphere = lateral surface area of cylinder
13. S
Proof
Surface area of a sphere
= Lateral surface area of a cylinder
= 2πrh
= 2πr(2r)
= 4πr^2
14. Surface area of a sphere = 4(πr^2)
We can also say that,
Surface area of sphere
= 4 times area of circle
15.
16. If a football of diameter 22 cm is
to be made then how much of
leather sheet will it need?
17. If a football of diameter 22 cm is to be made then how
much of leather sheet will it need?
Solution :
Given
Diameter = 22 cm
Radius = 11 cm
Surface area of a sphere = 4π(11)^2
= 4x3.14x121
= 1519.76 sq.units
