Learn the idea
Fractions can be added by counting same-sized parts. When the denominators differ, first rename both fractions using a common denominator. Keep the reference whole the same.
- Find a common multiple of the denominators.
- Rename both fractions by multiplying each numerator and denominator by the same number.
- Add the numerators, keep the common denominator, and simplify if possible.
LET’S WORK IT OUT
Worked example
Add 1/3 + 1/4.
4/12 + 3/12 = 7/12
Twelve is a common multiple of three and four. Four twelfths and three twelfths make seven twelfths.
A mistake to watch for
Adding both denominators gives a different part size. Add only the numerators after renaming.
Helpful skills to know first
YOUR TURN
Try three practice questions
Enter your answer, then check the explanation. You can also open each explanation to study it. These three questions check understanding; they are not a mastery score.
Question 1
Add 1/2 + 1/4. Enter a fraction.
Answer and explanation
3/4 — Rename one half as two fourths, then add one fourth.
Question 2
Add 1/3 + 1/6. Enter a fraction.
Answer and explanation
1/2 — Two sixths plus one sixth is three sixths, equivalent to one half.
Question 3
Add 2/5 + 1/10. Enter a fraction.
Answer and explanation
1/2 — Four tenths plus one tenth is five tenths, equivalent to one half.
For parents and teachers
Draw equal strips divided into twelfths to show both addends.
Ask your learner to explain the method before moving on. This lesson covers one focused skill and is not a complete curriculum assessment.