Ratios and Unit Rates
Aligned to 6.RP.A.3 — Common Core State Standards for Mathematics.
What this lesson teaches
A ratio compares two quantities. A unit rate tells you the amount per ONE — divide to find it, then you can scale to any amount.
Worked examples
Example 1
If 3 apples cost $1.50, the unit rate is $1.50 ÷ 3 = $0.50 per apple. So 10 apples cost 10 × $0.50 = $5.00.
Example 2
A 12 oz bottle costs $3.00 and a 20 oz bottle costs $4.60. Unit rates: $0.25/oz and $0.23/oz — the bigger bottle is the better deal.
Example 3
A recipe uses 2 cups flour to 3 eggs. To use 9 eggs, scale by 3: you need 6 cups of flour.
Practice questions
- A car goes 120 miles on 4 gallons. What's the miles-per-gallon?
- If 5 notebooks cost $7.50, what do 8 cost?
- Which is the better deal: 12 oz for $3 or 20 oz for $4.60?
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
Razones y Tasas Unitarias
Una razón compara dos cantidades. Una tasa unitaria te indica la cantidad por UNO: divides para encontrarla y luego puedes escalarla a cualquier cantidad.
Ejemplo 1: Si 3 manzanas cuestan $1.50, la tasa unitaria es $1.50 ÷ 3 = $0.50 por manzana. Entonces 10 manzanas cuestan 10 × $0.50 = $5.00.
Ejemplo 2: Una botella de 12 oz cuesta $3.00 y una de 20 oz cuesta $4.60. Tasas unitarias: $0.25/oz y $0.23/oz — la botella grande conviene más.
Ejemplo 3: Una receta usa 2 tazas de harina por 3 huevos. Para usar 9 huevos, multiplica por 3: necesitas 6 tazas de harina.
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