Signed Number Addition and Subtraction Demo
- Michael Shea
- Input two numbers in the input boxes.
- Press Show to see the numbers visualized as a vectors (arrows) on the number-line with a starting point at .
- The second number is shown slightly above the number-line for clarity.
- Press or to view an animation to visualize the sum or difference, respectively using the head-to-tail method.
- A copy of the second number is left on the screen in light green for reference.
- A perpendicular line from the end point of the second number is dropped to the number-line to show the result on the number line in red.
- Continue to press or to switch back and forth from addition and subtraction.
- When the second number is negative, note the following:
- The vector for the second number changes direction.
- An equation in black appears that shows how we handle addition and subtraction with negative numbers algebraically.
- Click Reset to remove the sum or difference visualization.
- The number-line is automatically scaled based on the numbers input.