Measuring with different units
Measure the length of an object using two different length units and describe how the measurements relate to the size of the unit chosen
What a learner can do afterwards
- Measure a desk in both centimetres and inches and compare the two numbers
- Explain that measuring with a smaller unit gives a larger number
- Predict whether a measurement in centimetres will be greater or less than in inches
The lesson
You already know how to measure things with a ruler. Did you know you can measure the very same object with two different units? The numbers you get will not match, even though the object stays exactly the same size.
Mia measures her desk with a centimetre ruler and counts to 100. Then she measures the same desk with an inch ruler and only counts to 39. The desk did not change size. Inches are a bigger unit, so she needed fewer of them.
Here is the rule: a smaller unit needs more copies to cover the same length, so it gives a bigger number. A bigger unit needs fewer copies, so it gives a smaller number.
Same object, different units: the smaller the unit, the bigger the number you count.
Watch it
Where it sits
Learn first
This opens up
Nothing builds on it yet.
Where this leads
8 questions wait behind this lesson, each with its answer explained. Every answer feeds the sky: stars light as they are learned, and dim when it is time to come back.