Fractions

In this lesson I will show you how to add, subtract, multiply, and divide fractions. Then I will show you how to simplify your answers.

Addition/Subtraction

These are done almost the same way. First, you find a common denominator (you need the same number on the bottom of both fractions). Then, you add or subtract across the top of the fractions and keep the bottom the same.

The hardest part of this is the common denominator. If you are good with numbers, you are trying to find the smallest number that both denominators can multiply to. If you are not good with numbers (don't know the times tables or need to use a calculator often), simply multiply the two bottom numbers. REMEMBER: whatever you do to the bottom you must also do to the top, and whatever you do to the top you must also do to the bottom.

I'll provide a few examples.

Watch carefully, the next example will be more condensed. With practice, you can begin to skip steps or do two steps as one.

Multiplication

This is the easiest. All you do is multiply across the bottom and across the top, no common denominator necessary.

Division

Dividing fractions requires a special technique: KEEP - CHANGE - FLIP. You KEEP the first (or top) fraction the same, CHANGE the division (or middle fraction line) to multiplication, and FLIP the second (or bottom) fraction. It sounds complicated, but the example will clarify.

Simplification

Now, once you have gotten everything down to a single fraction you still have work to do. Especially if your teacher tells you to simplify your fractions.

To do this, you must remove all common factors. In other words, you must divide the number on the top and the number on the bottom by the same number until there are no more numbers that you can do this with.