The word "fraction" means a "part of" something. We use numbers to explain how many parts we have. If you look at a fraction, you can tell how many parts there are in the whole, and how many of those parts we are talking about. For example, looking at the fraction "1/2,' what we can tell from this is that we have one of two parts. The bottom number of the fraction, which is called the denominator, tells us how many parts we have altogether. The top number, which is called the numerator, tells us how many of those parts we have.

Get out your ruler and examine it. A ruler is always 1 foot long.

Remember that 12 inches equals 1 foot. The ruler is broken into12 main parts. Each of those 12 parts is equal to 1 inch. So, the whole ruler is equal to 12 inches.

## Sciencing Video Vault

Remember that the bottom number of your fraction, the denominator, tells how many parts there are altogether. On a ruler, there are 12 parts (the 12 inches) altogether.

Get out a piece of paper, and trace a copy of your ruler. Mark all of the inches on your paper ruler where you see them on the real ruler.

Cut off 2 inches from your paper ruler. Count how many inches you have left. You can write this number as a fraction. You started with 12 inches, so that is your bottom number, telling how many parts altogether. The number of inches you have left is your top number--your numerator. It always tells how many parts of the whole you have.

Write the fraction "10/12." This fraction says that you have 10 parts out of 12. Think about the part that you cut off of your ruler. How could write that as a fraction? You cut off 2 inches from your ruler, so you have two parts. This is your numerator, and you always write it on top.

Write the fraction "2/12." Make a new paper ruler, and keep practicing with fractions until you feel confident that you know how to write them on your own.