Measurement & Data
Measuring with Non-Standard Units
Expressing the length of an object as a whole number of length units.
Prerequisites
- Ordering Objects by Length
Measuring with Everyday Objects
Comparing which object is longer works well for two or three objects, but it doesn't give an exact length. Measuring with a repeated unit — like paperclips laid end to end — gives length an actual number.
Definition — Length Unit
To measure this way, place copies of the same unit end to end along the object being measured, starting from one end, with no gaps between units and no overlapping. The length is the total number of units it took.
Worked Example — Measuring with Paperclips
Worked Example — Why the Same Unit Matters
Tip
Common Mistakes
Leaving small gaps between each unit while measuring, which undercounts the total length.
Push each unit right up against the end of the previous one, with no space in between, before placing the next unit.
Comparing two measurements made with different-sized units as if the numbers alone tell which object is longer, such as assuming 14 is more than 6 without noticing the units were different sizes.
A measurement only makes sense together with its unit. Compare lengths measured in the same unit, or convert to a shared unit before comparing.
Key Takeaways
- Measuring with a repeated unit gives length an exact number.
- Units must be placed end to end with no gaps and no overlaps.
- The same object measures a different number depending on the size of the unit used, so the unit always matters.
Summary
Measuring length with a repeated unit turns a comparison into an exact count. The next topic moves from measuring space to measuring time, and from counting objects to organizing information about a group.
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