When two variable quantities have a constant ratio, their relationship is called a direct variation. It is said that one variable varies directly as the other. The formula for direct variation is , where is the constant of variation.

Solve the equation for , the constant of variation.

Replace the variables and with the actual values.

Factor out of .

Cancel the common factors.

Factor out of .

Cancel the common factor.

Rewrite the expression.

Use the direct variation model to create the equation.

Substitute the value of into the direct variation model.

Simplify the result to find the direct variation equation.

Find the Equation that Relates x and y x=20 y=10