Learn how to combine and take away fractions — even when the denominators are different. We'll walk through each step, show you how it works visually, and then you can try it yourself!
A fraction has two parts. The numerator (top number) tells you how many parts you have. The denominator (bottom number) tells you how many equal parts make up the whole.
If a pizza is cut into 4 equal slices and you eat 3 of them, you've eaten 3/4 of the pizza.
When fractions already have the same denominator, adding is easy! Just add the numerators and keep the denominator the same.
Subtracting works the same way — subtract the numerators and keep the denominator:
You can't add or subtract fractions that have different denominators directly — it's like trying to add apples and oranges. You need to find a common denominator first so the pieces are all the same size.
A common denominator is a number that both denominators divide into evenly. The easiest one to use is the Least Common Denominator (LCD) — the smallest number that works.
Let's walk through an example step by step:
List multiples of each denominator until you find a match.
Multiples of 3: 3, 6, 9, 12, 15…
Multiples of 4: 4, 8, 12, 16…
The LCD is 12.
Multiply the numerator and denominator of each fraction by whatever turns the denominator into 12.
Now that the denominators match, add the numerators:
Subtracting works the same way — find the common denominator, build equivalent fractions, then subtract the numerators.
Multiples of 4: 4, 8, 12…
Multiples of 3: 3, 6, 9, 12…
The LCD is 12.
After adding or subtracting, check if your answer can be simplified (reduced). A fraction is simplified when the numerator and denominator have no common factors other than 1.
Both 4 and 6 can be divided by 2:
To simplify, find the Greatest Common Factor (GCF) of the numerator and denominator, and divide both by it.
Work through each problem step by step. Enter the common denominator, the equivalent numerators, and the final answer.
First, find the common denominator. Then fill in the equivalent fractions and your final answer.
Find the common denominator, fill in the equivalent fractions, then subtract.