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GeoGebraGeoGebra Classroom

Signed Number Addition and Subtraction Demo

Instructions:
  1. Input two numbers in the input boxes.
  2. 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.
  3. 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.
  4. Continue to press or to switch back and forth from addition and subtraction.
  5. 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.
  6. Click Reset to remove the sum or difference visualization.
  7. The number-line is automatically scaled based on the numbers input.