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# Finding Perimeter, Area, Volume, and Surface Area Study Guide: GED Math (page 2)

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### Finding Area

Area is a measure of the surface of a two-dimensional figure. The following table shows how to calculate the area of different figures.

### Finding Volume

Volume is a measure of the amount of space inside a three-dimensional shape. Three-dimensional shapes are sometimes called solids.

The formula for calculating the volume of a rectangular solid is:

V = Ah

where V = the volume

A = the area of the base

h = the height

Examples
1. Find the volume of a cube that is 3 inches long on each edge.
2. Choose the correct formula. The problem tells you that you are measuring the volume of a cube. The formula for the volume of a cube is V = Ah or V = s3.

Plug in the known measures and solve:

V = 33

= 3 × 3 × 3

= 27

So the final answer is 27 square inches.

3. Find the volume of a cylinder that has a height of 10 cm and a radius of 5 cm.
4. Choose the correct formula. The problem tells you that you are measuring the volume of a cylinder. The formula for the volume of a cylinder is V = Ah or V = πr2h.

Plug in the known measures and solve:

V = πr2h

= π(5)2(10)

= π(25)(10)

= π(250)

= 785

So the final answer is 785 cubic centimeters.

(Cubic centimeters can also be written as cm3.)

### Surface Area

The surface area of a three-dimensional object measures the area of each of its faces and adds them together. The total surface area of a rectangular solid is double the sum of the areas of the three different faces. For a cube, simply multiply the surface area of one of its sides by 6.

Practice problems for these concepts can be found at:

Geometry Practice Problems: GED Math

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