Tool & technique
Ruler
Compare lengths, draw straight lines, or help a fold find its edge.
Get to know it
A ruler can make a change visible without turning exploration into a test. Measure a bridge span or a shadow, then compare what happened after one change. Exact numbers are not always needed: a marked paper strip may help compare lengths when there is no ruler.
What happens if…
- What is useful to compare rather than measure exactly?
- How could you keep a record without a numbered scale?