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Surface area

Surface area of spheres

A sphere is a three-dimensional space, such as the shape of a football. A sphere is a body bounded by a surface whose every point is equidistant (i.e. the same distance) from a fixed point, called the centre or the origin of the sphere.

To find the total surface area of a sphere use the formula:

Surface area = 4πr2

What is the surface area of this sphere? Use π ≈ 3.14

Find the radius of the sphere.

radius = $\frac{1}{2}xdiameter=\frac{1}{2}x20=10$

Use this number in the surface area formula. Use π ≈ 3.14.

 Surface area
=
4
 π
 r
2

 4 × 3.14
×
 10 2

1,256

The surface area of the sphere is about 1,256 square millimeters.

What is the surface area of this sphere when r=4?

Use $\pi$=3.14