The total cost of gasoline varies directly with the number of gallons purchased. gas costs $1.89 per gallon. write a direct variation to the model the total cost c for g gallons of gas

The direct variation between the total cost c and the number of gallons g of the gas may be expressed as the following,
                                          c = kg
where k is the constant of variation. In this item, it is the cost of gasoline per gallon which is $1.89. Thus, the final variation equation is,
                                          c = 1.89g