The cost of the pencils (C) is directly proportional to the number of pencils (n). When the proportionality sign (∝) is replaced with an equal sign (=), the equation is \(x = k y\). The constant value ...

In this graph, 𝑥 and 𝑦 are directly proportional. This means that when 𝑥 doubles, 𝑦 also doubles, and when 𝑥 triples, so does 𝑦. In fact, for all coordinates on this line, you could multiply or ...

Twenty secondary mathematics teachers described their thinking as they solved four proportion problems (Task 1), explained how they would teach two of the problems (Task 2), and solved four similar ...