Fraction Word Problems
Aligned to 5.NF.A.2 — Common Core State Standards for Mathematics.
What this lesson teaches
To add or subtract fractions in a story, first estimate with easy benchmark fractions like 0, 1/2, and 1 to know about what to expect. Then rewrite the fractions with a common denominator and add or subtract. Check that your answer is close to your estimate.
Worked example
Maria ran 3/4 mile in the morning and 2/3 mile at night. How far total? Estimate: 3/4 and 2/3 are both a little under 1, so expect close to 1 1/2 miles. Now use denominator 12: 3/4 = 9/12 and 2/3 = 8/12. Add: 9/12 + 8/12 = 17/12 = 1 5/12 miles. That matches the estimate.
Practice questions
- A jug had 3/4 liter and you pour out 1/3 liter. How much is left?
- You read 2/5 of a book, then 1/2 more. How much have you read?
- Estimate first, then solve: 5/6 + 3/4. Is your answer more or less than 1 1/2?
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
Problemas con fracciones
Para sumar o restar fracciones en un problema, primero estima con fracciones de referencia fáciles como 0, 1/2 y 1 para saber más o menos qué esperar. Luego reescribe las fracciones con un denominador común y suma o resta. Verifica que tu respuesta esté cerca de tu estimación.
Ejemplo: María corrió 3/4 de milla en la mañana y 2/3 de milla en la noche. ¿Cuánto en total? Estima: 3/4 y 2/3 son ambos un poco menos de 1, así que espera cerca de 1 1/2 millas. Ahora usa el denominador 12: 3/4 = 9/12 y 2/3 = 8/12. Suma: 9/12 + 8/12 = 17/12 = 1 5/12 millas. Coincide con la estimación.
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