3.6 Small Group · Group 1
Tier 2 Intervention · Concrete-Representational-Abstract (CRA) · Dual-Language Anchors
Convert Measurements within the Same System · Conversion factor · Procedural Fluency · Real-World Applications
- Two measurements can only be compared when they are written in the same unit. Converting uses a special ratio — a unit ratio — that says how much of the smaller unit fits into exactly 1 of the larger unit. We'll walk through a worked example, try one together, then you'll try a few with hints right there when you need them.
- A ride requires riders to be at or above 44 inches tall. A child is 4 feet tall. The two measurements use different units, so I cannot compare them yet.
- Both units belong to the customary system, and there are 12 inches in one foot. That relationship is the conversion factor. As a ratio it is 12 : 1 — a unit ratio, because it compares an amount to exactly 1 foot.
- Inches are smaller than feet, so there will be MORE of them: I multiply. 4 × 12 = 48.
- The child is 48 inches tall. Now the comparison is fair: 48 inches is greater than 44 inches, so the child can go on the ride.
- Convert Measurements within the Same System (Convertir medidas dentro del mismo sistema) — Rewriting a measurement in a different unit of the SAME system, such as feet into inches or liters into milliliters.
- Conversion factor (Factor de conversión) — The ratio that links two units in the same measurement system, such as 12 inches to 1 foot. Within one system it is exact.
- Unit ratio (Razón unitaria) — A ratio that compares an amount to exactly 1 unit of another quantity, like 12 inches to 1 foot.
- Convert (Convertir) — To change a measurement from one unit to another without changing how much it is.
- Measurement system (Sistema de medidas) — A family of units that go together — customary units like inches and feet, or metric units like milliliters and liters.
- Double number line (Recta numérica doble) — Two number lines lined up so matching tick marks show two units for the same amount.
- A common mistake when converting within a measurement system is choosing the operation by habit instead of by unit size — multiplying every time. Converting 36 inches to feet by multiplying gives 36 × 12 = 432 feet, taller than a 40-story building. Ask first which unit is smaller: it takes MORE small units to make the same amount, so going to a smaller unit multiplies, and going to a larger unit divides.
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1 FILL TABLE
There are 4 cups in 1 quart. Complete the conversion table.
Quarts Cups 1 3 6 ✏️ Scratchpad / Reasoning -
2 FILL TABLE
There are 1,000 milliliters in 1 liter. Complete the double number line as a table.
Liters Milliliters 1 2 4 ✏️ Scratchpad / Reasoning
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3 MULTIPLE CHOICE
There are 12 inches in 1 foot. How many inches are in 5 feet?
- A60 inches
- B17 inches
- C7 inches
- D50 inches
✏️ Workspace & Solution Steps -
4 MULTIPLE CHOICE
There are 1,000 milliliters in 1 liter. How many milliliters are in 3 liters?
- A3,000 mL
- B1,003 mL
- C300 mL
- D30 mL
✏️ Workspace & Solution Steps -
5 MULTIPLE CHOICE
There are 16 ounces in 1 pound. How many pounds is 48 ounces?
- A3 pounds
- B64 pounds
- C768 pounds
- D32 pounds
✏️ Workspace & Solution Steps -
6 MULTIPLE CHOICE
A child is 4 feet tall. A ride requires 44 inches. Can the child ride?
- AYes, because 4 feet = 48 inches, which is more than 44
- BNo, because 4 is less than 44
- CYes, because 4 feet = 44 inches exactly
- DYou cannot compare feet and inches
✏️ Workspace & Solution Steps
Group Discussion Prompt: How does your visual model justify your mathematical solution?
Partner A: "I modeled this by identifying the relationship and..."
Partner B: "I agree with your step because the standard mathematical rule states..."
Complete each sentence stem to demonstrate precise mathematical reasoning:
Writing Task: Justify why your mathematical solution is accurate and complete.