Chapter 8.7, Problem 46SR

To determine

To calculate: To write an equation that could be used to find the unit cost of a gallon of gas. Then find the unit cost.

Answer to Problem 46SR

Equation to find the unit cost of a gallon of gas is $Unitcost=\frac{y}{x}$

Unit cost of a gallon of gas is $\$2.75$

Explanation of Solution

Given information: The cost of gas varies directly with the number of gallons bought. Marty bought $18$ gallons of gas for $\$49.50$

Calculation:

Let the cost of $x$ gallons of gas is $\$y$ .

Thus, equation to find the unit cost of a gallon of gas is calculated as follows:

  $Unitcost=\frac{y}{x}$

Substituting the values in above equation to get the unit cost

  $\begin{array}{l}Unitcost=\frac{49.50}{18}\\ Unitcost=2.75\end{array}$

Hence, equation is $Unitcost=\frac{y}{x}$ and unit cost is $\$2.75$