Proportional Relationships

Straight lines through the origin

An interactive lesson with 6 steps, about 5 minutes: you predict, drag and solve, with instant feedback on every answer. It runs in your browser and needs JavaScript.

What you’ll learn

• Proportional: $y = kx$, with a constant ratio $k$ (the unit rate).
• The graph is a straight line through the origin.
• A fixed fee breaks proportionality, even if the graph is straight.

Steps

1. Double one, double the other
2. Find the rate
3. Proportional or not?
4. Use the constant
5. Scaling a recipe
6. Exchange rates