Question

Suppose you want to determine the number of miles you can drive in your car. Your car gets 28 miles per gallon. The number of miles traveled varies directly with the number of gallons of gas the tank holds. Write the direct variation equation that represents this situation. Let y be the dependent variable and let x be the independent variable.

Answer 1

Direct variation is of the form y=kx, where k is the constant of variation.  It is "direct" because as x increases/decreases so does y in the same magnitude.

y=kx,  In this case the dependent variable y, is miles and the independent variable x, is gallons.  We are told that the car gets 28mi/gal so

y=28x