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Sphere is nothing but a any type of ball. As it is in circular shape so it has diameter and radius.

OP is the radius of the sphere.

Sphere :Surface area (TSA) = CSA = 4πr ^{2}Hemisphere :Curved surface area(CSA) = 2 π r ^{2}Total surface area = TSA = 3 π r ^{2} |

1) The radius of hemispherical balloon increase from 7 cm to 14 cm as air is being pumped into it. Find the ratios of the surface areas of the balloon in two cases.

For 1st hemisphere, r = 7 cm

TSA -1 = 3 π r

⇒ = 3 x π x 7

TSA-1 3 π x 7^{2} 1-------- = --------- = ---- TSA -2 3π x 14 ^{2} 4 |

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2) Show that the surface area of sphere is same as that of the lateral surface area of a cylinder that just encloses the sphere.

Total surface area of sphere = 4 π r

The radius and height of the cylinder that just encloses the sphere of radius r and 2r respectively.

∴ CSA of cylinder = 2 π r h

⇒ = 2 π r x 2r

∴ CSA of cylinder = 4 π r

∴ From (1) and (2)

Surface area of sphere is same as that of the lateral surface area of a cylinder that just encloses the sphere.

• Surface Area of Cube

• Surface Area of Rectangular Prism(Cuboid)

• Surface Area of Cylinder

• Surface Area of Cone

• Surface Area of Sphere and Hemisphere

• Surface Area of Prism

• Surface Area of Pyramid

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