Adding Fractions with Unlike Denominators
Aligned to 5.NF.A.1 — Common Core State Standards for Mathematics.
What this lesson teaches
You can only add fractions when the pieces are the same size. Rewrite both fractions with a common denominator (a shared multiple), then add the numerators and keep the denominator.
Worked example
1/3 + 1/4 → common denominator 12. 1/3 = 4/12 and 1/4 = 3/12. Add: 4/12 + 3/12 = 7/12.
Practice questions
- Add 2/5 + 1/3.
- Subtract 3/4 − 1/6.
- Why can't you just add 1/3 + 1/4 to get 2/7?
Watch the lesson
Every lesson comes with a video taught in English and Spanish — the same video the QR code in the printed workbook opens.
▶ Watch this lessonEn español
Suma de fracciones con denominadores diferentes
Solo puedes sumar fracciones cuando las partes tienen el mismo tamaño. Reescribe ambas fracciones con un denominador común (un múltiplo compartido), luego suma los numeradores y conserva el denominador.
Ejemplo: 1/3 + 1/4 → denominador común 12. 1/3 = 4/12 y 1/4 = 3/12. Suma: 4/12 + 3/12 = 7/12.
More Number & Operations—Fractions lessons
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