How to teach the number line

Kindergarten to Grade 3

A number line is a straight line with numbers marked at equal spaces. It turns numbers into positions and distances, which makes counting, comparing, adding, subtracting and rounding visual. Because the spacing is even, the gap between marks always stands for the same amount, and that even spacing is the key idea.

How to teach it

1. Start with a marked, evenly spaced line and read the labelled points before finding unlabelled ones.
2. Teach that equal gaps mean equal steps: count the intervals (the jumps), not the marks, to measure a distance.
3. Find a missing number by working out the step size from two known marks, then counting on.
4. Model addition as jumps to the right and subtraction as jumps to the left, landing on the answer.
5. Use it for rounding and comparing: a number is nearer whichever labelled mark it sits closer to.

Common mistakes

• Counting the marks instead of the gaps when measuring a jump.
• Assuming the line starts at zero or steps up in ones without checking the labels.
• Spacing numbers unevenly when drawing a line of their own.
• Losing the step size when the marks go up in 2s, 5s or 10s.