Learn it
You can only add pieces of the same size. To add 1/3 + 1/4, rename both fractions with a common denominator. The least common multiple of 3 and 4 is 12.
1/3 = 4/12 and 1/4 = 3/12, so 1/3 + 1/4 = 7/12.
Steps: find a common denominator → rename each fraction → add the numerators → simplify.
Worked examples
Example 1
Add 2/5 + 1/2.
- Common denominator 10
- 2/5 = 4/10, 1/2 = 5/10
- 4/10 + 5/10 = 9/10
Answer: 9/10
Example 2
Add 5/6 + 3/4.
- Common denominator 12
- 5/6 = 10/12, 3/4 = 9/12
- 19/12 = 1 7/12
Answer: 1 7/12
Practice
Try these on paper first, then check your work.
- 1/2 + 1/6
- 3/8 + 1/4
- 2/3 + 1/5
- 7/10 + 1/2
Show the answer key
- 4/6 = 2/3
- 5/8
- 13/15
- 12/10 = 1 1/5