Mixed number

Imagine you have three pizzas on your table, one cheese pizza, one salami pizza, and then the best pizza in the world, Pizza Hawaii:

If we didn't want to use the word "three", we could write that there are 3 pizzas on the table. Now, let's say we eat three slices of Hawaiian pizza. How many pizzas do we have left?

We can see that we have two whole pizzas left, and we have five pieces of the third pizza left out of eight. How would we write that down as a number? We can use mixed numbers, in which we mix together whole numbers and add fractions. So we can say that we have left

$$2\frac{3}{8}$$

of pizzas. A composite number is made up of two parts: first the whole number, followed by the fraction. There is no operator, no sign, between the integer and the fraction. Note that if you added a period $2\cdot\frac38$, it would not be a composite number, but the product of the integer and the fraction. So the mixed number has the form

$$a\frac{b}{c}$$

and its value is equal to

$$a + \frac{b}{c}.$$

We only write numbers that are greater than one as a mixed number. For example, if you only have half of one pizza, we don't use the notation $0\frac12$. We only use the notation $\frac12$. Similarly, we don't use mixed numbers for negative numbers.