If you scale up x by a certain amount and y gets scaled up by the same amount, then it's direct variation. If you scale up x by some-- and you might want to try a couple different times-- and you scale down …

Sal gives many examples of two-variable equations where the variables vary directly, inversely, or neither.

Direct variation. So if y varied directly with x it literally means that y is equal to some constant multiple of x, or if you divide both sides of this by x it means that y over x is equal to k so the ration between y …

Now, depending on the situation it can be a lot of things. For instance, the number of soda cans you buy and the price you pay are in direct variation; here, k would be the price of one can. In terms of the …

Direct variation. So if y varied directly with x it literally means that y is equal to some constant multiple of x, or if you divide both sides of this by x it means that y over x is equal to k so the ration between y …

Given a few two-variable equations, find those that show direct or inverse variation.

Worked example: Model a context about filling gas with a direct variation equation. Created by Sal Khan and Monterey Institute for Technology and Education.

Learn about direct variation, its properties, and how to solve related problems with step-by-step instructions on Khan Academy.

Sal models a context about lengths of strings and the frequency of their vibrations! with an inverse variation equation. Created by Sal Khan and Monterey Institute for Technology and Education.

This is direct variation because one variable, y, varies directly with the other variable, x, which is scaled by a constant, k. y=k*1/x is the only form of inverse variation, although it can look quite different …