Common fractions are most often written in their simplest form. This is also known as expressing or writing fractions using the lowest terms.
Common fractions can be simplified to their lowest terms by applying the concept of equivalent fractions.
If necessary, review equivalent fractions with your child before working on simplifying common fractions.
Equivalent Fractions: Recap
Look at the four fractions below. They are all equivalent to each other.
Note how the numerator and denominator both increase by a factor of 2 each time.
Multiplying or dividing both the numerator and denominator by the same number does not change the amount the fraction represents; it only changes how the fraction is written.
Here is another example of equivalent fractions.
In this case the numerator and denominator both decrease by a factor of 3
Simplifying fractions: using common factors
Simplifying fractions means dividing the top and bottom by the same number so that the top and bottom become as small or as simple as possible.
To simplify a common fraction we can find the greatest common factor for the numerator and the denominator and then use it to divide both. The steps below show an example of how to do this:
|What is the fraction?||16/20|
|Find the factors of 16 (the numerator)||1 , 2 , 4 , 8 , 16|
|Find the factors of 20 (the denominator)||1 , 2 ,4 , 5 , 10 , 20|
|Find the common factors||1 , 2 , 4|
|Find the greatest common factor||4|
|Divide 16 (the numerator) by 4||16 ÷ 4 = 4|
|Divide 20 (the denominator) by 4||20 ÷ 4 = 5|
|Write the fraction in simplest form||4/5|
trial and error, exploration
When simplifying fractions you can use a trial and error method as an alternative to the greatest common factor one that is shown above .
- Ask yourself, what is the largest whole number that you can think of that both the top and bottom (numerator and denominator) are divisible by.
- Divide both by this number.
- Keep asking yourself the same question until the only number that both are divisible by is 1
The following examples show how this trial and error method can be used while simplifying fractions.
Example: Simplifying 16/24
|What number are the
top and bottom both divisible by?
|2||Divide top and bottom by 2 to get 8/12||Not yet..keep going..|
|Same question as above||2||Divide top and bottom by 2 to get 4/6||Not yet..keep going..|
|Same question as above||2||Divide top and bottom by 2 to get 2/3||Yes|
If we had tried dividing by 4 or even 8 on our first try we would have simplified the fraction sooner. Not to worry though, we got there in the end!
Example: Simplifying 48/60
|What number are the top and bottom both divisible by?||6||Divide top and bottom by 6 to get 8/10||Not yet..keep going..|
|Same question as above||2||Divide top and bottom by 2 to get 4/5||Yes|
Example: Simplifying 60/100
|What number are the top and bottom both divisible by?||10||Divide top and bottom by 10 to get 6/10||Not yet..keep going..|
|Same question as above||2||Divide top and bottom by 2 to get 3/5||Yes|
Common error when simplifying fractions
The example below shows a fairly common error made by students when showing fractions in their simplest form.
In fairness to those that make the “error” above, if just asked to “simplify a fraction” then the answer above is not wrong – it is just not as good an answer as the correct one!
Use the Simplifying Fractions Worksheet Generator to get as much practice as you need.
The worksheet below will also provide practice on simplifying fractions..
- Simplifying Fractions e.g. 4/10 = 2/5
Here is a very nice and simple explanation of simplifying fractions from Math is Fun.