# 007 - 008 Volume and surface area of earth and balloon

**Example 007**

A spherical balloon is inflated so that so that its diameter is 12 m. Find the surface area of the balloon’s covering and the volume of the gas.

**Solution 007**

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Surface area of the balloon

$A = \pi D^2 = \pi(12^2)$

$A = \pi D^2 = \pi(12^2)$

$A = 452.39 \, \text{ m}^2$ *answer*

Volume of gas

$V = \frac{1}{6}\pi D^3 = \frac{1}{6}\pi (12^3)$

$V = 904.78 \, \text{ m}^3$ *answer*

**Example 008**

Find the volume and total surface area of the earth. (Consider the earth a perfect sphere of diameter 7960 miles.)

**Solution 008**

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Surface area of the earth

$A = \pi D^2 = \pi (7960^2)$

$A = \pi D^2 = \pi (7960^2)$

$A = 199.06 \times 10^6 \, \text{ miles}^2$ *answer*

Volume of gas

$V = \frac{1}{6}\pi D^3 = \frac{1}{6}\pi (7960^3)$

$V = 2.64 \times 10^{11} \, \text{ miles}^3$ *answer*

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