Idea 3of 22Builds onPick a unit that fits the size
Rough or exact: the job picks the unit
Is the same gap always measured in the same unit?
Today you'll discover
- when a rough reading is enough
- when you need small units
- how the job decides
Think firstCutting a board to fit a shelf gap
You will cut a board to fit this gap exactly. Which reading do you need?
Decide first, then press Next. Ask: why am I measuring it?
A drawing of two shelf sides with a dashed gap between them. Down the right, the gap written three ways: about 1 m (rough: fine for talking), 107 cm (close, but not exact) and 1072 mm (exact, to the millimetre). The millimetre line is ringed. The last step shows the walk to school written as about 1 km, 1140 m and 114 000 cm.
See the whole ideathe big idea and the key word, in one place
The big idea
Rough jobs can use big units; exact jobs need small units.
Compare themRough: about how far the park is. Exact: the size of the glass for a picture frame.
Easy to get wrongA rough reading says “about”. An exact reading drops the “about” and uses a smaller unit.
Key word
- precise
- exact, measured to a small unit such as the millimetre
Ready to use it?
- Pick the reading that fits a job: rough or exact.