Use the image to answer the question.
An illustration shows two graphs depicting cost of gasoline per gallon in dollars in store A and B. The first graph shows cost of gasoline per gallon in dollars in store A. The horizontal axis shows gallons ranging from 0 to 20 in increments of 5. The vertical axis shows the cost in dollars ranging from 0 to 70 in increments of 10. Four data points are plotted on the graph at left parenthesis 0 comma 0 right parenthesis, left parenthesis 5 comma 20 right parenthesis, left parenthesis 10 comma 40 right parenthesis, and left parenthesis 15 comma 60 right parenthesis. A line connects all the data points. The second graph shows cost of gasoline per gallon in dollars in store B. The horizontal axis shows gallons ranging from 0 to 10 in increments of 2. The vertical axis shows the cost in dollars ranging from 0 to 30 in increments of 2. Three data points are plotted on the graph at left parenthesis 0 comma 0 right parenthesis, left parenthesis 4 comma 14 right parenthesis, and left parenthesis 8 comma 28 right parenthesis. A line connects all the data points.
The proportional relationship between the cost of gasoline and the number of gallons of gasoline from Store A and Store B are displayed in the graphs. Use the graphs to interpret the store that has the cheaper cost of gasoline per gallon.
Based on the graphs, store B has the cheaper cost of gasoline per gallon. The line connecting the data points in store B is lower on the graph compared to the line in store A, indicating a lower cost for each gallon of gasoline purchased.
To determine the store that has the cheaper cost of gasoline per gallon, we need to compare the slopes of the lines on the two graphs.
In the first graph, the line connecting the data points shows that the cost of gasoline per gallon in Store A increases by $20 for every 5-gallon increase. This can be calculated as:
Change in cost / Change in gallons = ($40 - $20) / (10 - 5) = $20 / 5 = $4 per gallon.
In the second graph, the line connecting the data points shows that the cost of gasoline per gallon in Store B increases by $14 for every 4-gallon increase. This can be calculated as:
Change in cost / Change in gallons = ($28 - $14) / (8 - 4) = $14 / 4 = $3.5 per gallon.
Comparing the two slopes, we can see that the cost of gasoline per gallon in Store B is cheaper ($3.5) compared to Store A ($4). Therefore, Store B has the cheaper cost of gasoline per gallon.