determine the constant of proportionality (k = y/x) within mathematical and real-world problems

What's the Constant of Variation?

The constant of variation is the number that relates two variables that are directly proportional or inversely proportional to one another. But why is it called the constant of variation? This tutorial answers that question, so take a look!
What's the Formula Connecting Distance, Speed, and Time?

When you have constant speed, the same formula pops up over and over again, and that's the formula that connects distance, speed, and time. Make sure you know this formula, and if you want a refresher, check out the tutorial!
What's the Direct Variation or Direct Proportionality Formula?

Ever heard of two things being directly proportional? Well, a good example is speed and distance. The bigger your speed, the farther you'll go over a given time period. So as one variable goes up, the other goes up too, and that's the idea of direct proportionality. But you can express direct proportionality using equations, and that's an important thing to do in algebra. See how to do that in the tutorial!
How Do You Find the Rate of Change Between Two Points on a Graph?

The rate of change is a rate that describes how one quantity changes in relation to another quantity. In this tutorial, practice finding the rate of change using a graph. Check it out!
How Do You Use a Sample to Make Predictions About a Population?