## Volume

Volume is a measurement of the amount of space that 3-d objects holds. For example, if a question on the GED math test asked you to calculate the volume of a cup, you can’t just say how many ounces it holds. You need to say how many cubes of a unit, like cubic inches, fit into the cup. For this reason volume is always represented in cubic units, such as 5 yards³.

## Volume of a Cube

Volume = edge³

To find the volume of a cube, just cube the length of the edge. Cubing something just means multiplying it by itself two times. In the example above you would just multiply 5 by itself two times:

5³ = 5 x 5 x 5 = 125 in.³ (or 125 cubic inches)

## Volume of a Rectangular Container

Volume = length x height x width

To find the volume of a rectangular container, multiply its length by its height by its width. If you were asked to find the volume of the above rectangular solid, just multiply 4 by 2 by 1.5.

4 x 2 = 8

8 x 1.5 = 12

volume = 12 ft.³

## Volume of a Cylinder

Volume = π x radius² x height

To find the volume of a cylinder, square the radius, multiply that by the height, and multiply that by pi.

2² = 4

4 x 4 = 16

16 x π (3.14) = 50.24

v = 50.24 cm³

## Volume of a Pyramid

Volume = 1/3 x (base edge)² x height

To find a square base pyramid’s volume, first square the length of one of its base sides, multiply that by its height, and multiply that number by a third (1/3).

3² = 9

9 x 5 = 45

45 x 1/3 = 15

v = 15 ft³

## Volume of a Cone

Volume = 1/3 x π x radius² x height

Square the radius, multiply that by the cone’s height, multiply by pi, then multiply by 1/3.

3² = 9

9 x 7 = 63

63 x π (3.14) = 197.82

197.82 x 1/3 = 65.94

v = 65.94 cm³

Share and Enjoy:

1. Zach says:

I’m taking my GED tomorrow – the Math portion in the morning. I hope I pass. Your website has helped me a lot. Volume and everything is one of my weakest points.

• Ziyi says:

Good luck, Zack! I’m sure you’ll do great!

• Megan Trotter says:

did you pass your test?

• Paul says:

I don’t think the person did..otherwise I would imagine they would’ve responded..
I’m taking mine on the 13th or 14th of this month…I missed it by a point…
There’s one question about a birdhouse..it gives you the dimensions minus the hole for the front and at the end asks you to find out how big a piece of wood you’d need to cut out all the shapes..in approximate not around

2. sandiin says:

how do you times with the 1/3

• Ziyi says:

Check here to see how to multiply fractions:

http://www.math4ged.com/multiplying-and-dividing-fractions/

Also, you can use the calculator that is issued to you during the test to multiply fractions.

A third thing you could do is just to use .33 instead of 1/3. This won’t give you an exact answer, but since the test is mostly multiple choice just choose the closest one and you’ll get it right.

3. nanzina says: