Units and Scale
Aligned to N-Q.A.1 — Common Core State Standards for Mathematics.
What this lesson teaches
Units tell you what a number means and how quantities combine; carry them through every step and cancel them like factors. On a graph, the scale and origin decide how large or steep the data appears.
Worked examples
Example 1
A car travels 150 miles in 3 hours. Divide to find the rate: 150 miles / 3 hours = 50 miles/hour. The units mi/h confirm the result is a speed.
Example 2
Convert 60 mi/h to ft/s: 60 × 5280 ÷ 3600 = 88 ft/s. Carry the units and they cancel to the ones you want.
Example 3
If the units come out wrong, the arithmetic is wrong. Dividing miles by miles per hour gives hours, which is how you catch a flipped fraction.
Practice questions
- A recipe uses 2 cups of flour for 12 cookies. Find cups per cookie.
- Convert 90 km/h to kilometers per minute.
- A graph's y-axis starts at 50 instead of 0. Explain how that could make a small change look large.
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
Unidades y Escala
Las unidades te dicen qué significa un número y cómo se combinan las cantidades; llévalas en cada paso y cancélalas como factores. En una gráfica, la escala y el origen deciden qué tan grande o inclinado se ve el dato.
Ejemplo 1: Un carro recorre 150 millas en 3 horas. Divide para hallar la razón: 150 millas / 3 horas = 50 millas/hora. Las unidades mi/h confirman que el resultado es una rapidez.
Ejemplo 2: Convierte 60 mi/h a ft/s: 60 × 5280 ÷ 3600 = 88 ft/s. Arrastra las unidades y se cancelan hasta dejar las que quieres.
Ejemplo 3: Si las unidades salen mal, la aritmética está mal. Dividir millas entre millas por hora da horas, y así atrapas una fracción volteada.
More Number & Quantity lessons
Teach this lesson today
An AI tutor that guides with questions instead of just giving answers — all K–12 core subjects, every child in the family.
Start free — no card required