Volume of sphere — lesson. Mathematics CBSE, Class 9.

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Sphere:

A sphere is a three-dimensional figure obtained by the revolution of a semicircle about its diameter as an axis.

Volume of a sphere:

Let

$r$ be the radius of a sphere.

Volume of a sphere

$=$

$\frac{4}{3} π r^{3}$ cu. units

Example:

Find the mass of

$5$ spherical balls, each of diameter

$8.4$

$cm$ .

Solution:

Diameter of the spherical ball

$(d)$

$=$

$8.4 \ cm$

Radius of the spherical ball

$(r)$

$=$

$\frac{d}{2} = \frac{8.4}{2} = 4.2$

$cm$

Volume of the spherical ball

$=$

$\frac{4}{3} π r^{3}$ cu. units

$=$

$\frac{4}{3} \times \frac{22}{7} \times {(4.2)}^{3}$

$=$

$\frac{4}{3} \times \frac{22}{7} \times 4.2 \times 4.2 \times 4.2$

$=$

$310.464$

Volume of the spherical ball is

$310.464 \ cm^3$ .

Volume of

$5$ spherical balls:

$=$

$310.464 \times 5$

$=$

$1552.32$

Therefore, the volume of

$5$ spherical balls is

$1552.32 \ cm^3$ .

Important!

The value of

$\pi$ should be taken as

$\frac{22}{7}$ unless its value is shared in the problem.

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1. Volume of sphere

Theory: