Number Line
Watch addition and subtraction as jumps along the number line — including crossing zero into negative numbers.
About the Number Line
Addition and subtraction make more sense as movement once a student can see it happen rather than just compute it. This tool places a starting value on a number line and animates the operation as a series of hop arcs, one per unit, moving right for addition and left for subtraction, landing on the result with its own marker.
The line's range adjusts automatically to fit whatever numbers are in play, including negative starting points, so the same tool works for early addition within 20 and for introducing negative numbers later on.
How to use it in your classroom
- Set the starting value with the slider, including negative numbers if needed.
- Choose the operation: + or −.
- Set the amount being added or subtracted with the second slider.
- Read the hop arcs moving across the number line from the start value to the result, then check the final equation displayed below.
Tips from the classroom
- Start with small amounts (1-3) so individual hop arcs are easy to count one at a time before moving to larger jumps.
- Use a negative starting value paired with addition to show how a sum can still land on the negative side of zero — it's a clearer visual than a worked equation alone.
- Pause after setting the values and ask students to predict the result before watching the hops resolve.
- Switch the operation between + and − with the same start and amount to highlight how the direction of the hops is the only thing that changes.
Frequently asked questions
Can the starting value or result be negative?
Yes, the number line range expands automatically to include negative numbers whenever the starting value or the result requires it.
What's the largest amount I can add or subtract in one step?
The amount slider goes up to 12, which keeps the hop arcs readable as individual jumps rather than a blur of overlapping lines.
Does each hop represent one unit, or does it scale with the total amount?
Each hop is always exactly one unit, so the number of arcs drawn always matches the amount you set.