Fractions

Writing fractions

Every fraction has two parts: a top number and a bottom number. In math terms, these are called the numerator and the denominator. Don't worry too much about remembering those names. As long as you remember what each number means, you can understand any fraction.

As you saw in the slideshow, the bottom number, or denominator, is the number of parts a whole is divided into. In our pizza example, we said each slice was 1/8 of the pizza. The denominator was 8, since the pizza was divided into 8 slices.

The top number, or numerator, refers to a certain number of those parts. It lets us know how much we're talking about. Since we're talking about one slice of pizza, our numerator is 1.

Let's look at another example. What if we divided the same pizza into 12 slices instead of 8? If we took one slice, that would be 1/12 of the pizza—1 slice out of the 12 total slices. No matter what fraction you're trying to write, you always write it the same way—with the number of parts on the bottom, and the parts you're referring to on top.

Now you try it. Write these images as fractions.

Reading fractions

In the example above, if you had a pizza with eight slices, each slice would be 1/8 of the pizza. You'd read that like this: one-eighth.

When we read or talk about fractions, we use special numbers called ordinal numbers. A good way to remember this is that many of them are the same numbers you use when you're putting things in order: third, fourth, fifth, and so on.

You might know some of these numbers already. For example, when you tell your boss you'll be at work in half an hour, you're saying that you'll get there in 1/2 of an hour. If you're helping a friend bake a cake and she asks you for a third of a cup of sugar, you might know to hand her the measuring cup that says 1/3.

Here are some of the most commonly used fractions:

 A good rule to remember is that most ordinal numbers end in "th." So, 1/20 is one-twentieth. 1/35 is one-thirty-fifth. 1/54 is one-fifty-fourth.

What about fractions that don't have a 1 on top? Read these as if you were counting. So if 1/5 is one-fifth, then 2/5 is two-fifths, and 3/5 is three-fifths. The top number will always be a "normal" number like the ones you use to count, and the bottom number is always an ordinal number.

Now you try it. Write fractions to match the text.

Mixed numbers

Sometimes you might see a fraction next to a whole number. We call this a mixed number. We'll talk more about mixed numbers in the next lesson. For now, we'll concentrate on learning how to read them. Let's take a look at this example: 

2 1/2 is a mixed number. If we say we have 2 1/2 pizzas, it means we have 2 whole pizzas and 1/2 of another pizza. You can read 2 1/2 like this: two-and-a-half.

Let's try another example. What if you pour 1 whole cup of tea, then fill only 2/3 of another cup? You could write that situation like this:

You'd read 1 2/3 like this: one and two-thirds. Remember, the whole number is always first.

Now it's your turn. Write the correct mixed number under each picture.