**This is the students’ version of the page. Log in above for the teachers’ version.**

Prerequisites

- A knowledge of the four operations from lessons N2a, N2b, N2c, N2d, N2e and N2f is assumed.
- A17a – Solving simple linear equations in one unknown algebraically
- A17c – Finding solutions to linear equations using graphs
- A11a – Identifying roots, intercepts and turning points of quadratic functions graphically

# An illustration of quantities in direct proportion

Adjust the dark grey slider to select the cost of 1 metre of rope. Now in this example, **the cost of a piece of rope is directly proportional to its length**. The longer the rope, the more it will cost. What happens to the cost if you double the length of rope? What if you triple the length? Investigate by adjusting the blue and green sliders.

# Direct proportion in other contexts: currency conversions and imperial-metric conversions

# Solving problems involving direct proportion

In the real world

**Teachers**: log in to view this content.