Fractions: Adding and Subtracting
A fraction represents a part of a whole. To add or subtract fractions, they must have the same denominator — the common denominator. If they don't, find the least common multiple (LCM) of the denominators first. Then add or subtract the numerators.
Key Concepts
Like vs. Unlike Denominators
Like denominators: 3/8 + 2/8 = 5/8 — easy, just add numerators. Unlike denominators: 1/3 + 1/4. Find LCM of 3 and 4 = 12. Convert: 4/12 + 3/12 = 7/12. You must always convert to a common denominator before adding or subtracting.
Mixed Numbers
A mixed number has a whole part and a fraction: 2¾. To add mixed numbers, add the whole parts and fraction parts separately. If the fraction part exceeds 1, convert the extra to a whole number: 1⁴⁄₃ = 2⅓.
Simplifying (Reducing) Fractions
Always simplify your answer. Find the GCF (Greatest Common Factor) of numerator and denominator and divide both. 6/8 → GCF is 2 → 3/4. A fraction is fully simplified when the GCF is 1.
🆕 Fraction Calculator
Add or subtract any two fractions. See the common denominator step!
✅ Check Your Understanding
1. What must you find before adding unlike fractions?
2. What is 1/2 + 1/3?
3. What is the GCF of 8 and 12?