Selecting Appropriate Units of Measurement
Selecting Appropriate Units of Measurement teaches Grade 6 students to choose measurement units that produce sensible, manageable numerical values — units whose scale is close to the size of the object being measured. Covered in Illustrative Mathematics Grade 6, Unit 3: Rates and Percentages, this practical skill prevents awkward measurements like expressing a room width in kilometers or a molecule size in miles. Students consider the magnitude of the object and select units that make the numerical measure reasonable.
Key Concepts
To select an appropriate unit of measurement, choose a unit that is on a similar scale to the object. If an object's size is $S$, and $S = M \times U$ where $M$ is the numerical measurement and $U$ is the unit, the goal is to choose $U$ so that $M$ is a convenient, easy to understand number.
Common Questions
How do you select an appropriate unit of measurement?
Choose a unit that is on a similar scale to what you are measuring, so the numerical value is a reasonable size — not too large or too small.
Why would you not measure a room in millimeters?
The number would be extremely large (a 4-meter room is 4000 mm), making it hard to interpret and work with. Meters or feet are more appropriate.
What unit should you use to measure the distance between cities?
Kilometers or miles are appropriate for long distances. Using meters would give very large, unwieldy numbers.
Where is selecting appropriate units in Illustrative Mathematics Grade 6?
This concept is in Unit 3: Rates and Percentages of Illustrative Mathematics Grade 6.
How do you convert between units if you chose the wrong one?
Use unit conversion factors. Multiply or divide by the conversion ratio between the two units to change to a more appropriate unit.