Multiplying Fractions
Multiply the tops, multiply the bottoms.
There are 3 simple steps to multiply fractions1. Multiply the top numbers (the numerators). 2. Multiply the bottom numbers (the denominators). 3. Simplify the fraction if needed. |
Example:
| 1 | × | 2 |
| 2 | 5 |
Step 1. Multiply the top numbers:
| 1 | × | 2 | = | 1 × 2 | = | 2 |
| 2 | 5 |
Step 2. Multiply the bottom numbers:
| 1 | × | 2 | = | 1 × 2 | = | 2 |
| 2 | 5 | 2 × 5 | 10 |
Step 3. Simplify the fraction:
| 2 | = | 1 |
| 10 | 5 |
With Pizza
Here you can see it with pizza ...
... and do you see how two-tenths is simpler as one-fifth?
With Pen and Paper
And here is how to do it with a pen and paper (press the play button):
Another Example
| 1 | × | 9 |
| 3 | 16 |
Step 1. Multiply the top numbers:
| 1 | × | 9 | = | 1 × 9 | = | 9 |
| 3 | 16 |
Step 2. Multiply the bottom numbers:
| 1 | × | 9 | = | 1 × 9 | = | 9 |
| 3 | 16 | 3 × 16 | 48 |
Step 3. Simplify the fraction:
| 9 | = | 3 |
| 48 | 16 |
(This time we simplified by dividing both top and bottom by 3)
The Rhyme
♫ "Multiplying fractions: no big problem,
Top times top over bottom times bottom.
"And don't forget to simplify,
Before it's time to say goodbye" ♫
Fractions and Whole Numbers
What about multiplying fractions and whole numbers?
Make the whole number a fraction, by putting it over 1.
| Example: 5 is also | 5 |
| 1 |
Then continue as before.
Example:
| 2 | × | 5 |
| 3 |
Make 5 into 5/1 :
| 2 | × | 5 |
| 3 | 1 |
Now just proceed as normal.
Multiply tops and bottoms:
| 2 | × | 5 | = | 2 × 5 | = | 10 |
| 3 | 1 | 3 × 1 | 3 |
The fraction is already as simple as it can be.
| Answer = | 10 |
| 3 |
Or you can just think of the whole number as being a "top" number:
Example:
| 3 | × | 2 |
| 9 |
Multiply tops and bottoms:
| 3 | × | 2 | = | 3 × 2 | = | 6 |
| 9 | 9 | 9 |
Simplify:
| 6 | = | 2 |
| 9 | 3 |
Mixed Fractions
You can also read how to multiply mixed fractions