CPM Homework Help : GB8I Problem 1-18

In December of 2003, the average price for a gallon of regular gas in the United States was $$1.50$ .

At that time, what did it cost to buy $12$ gallons of gas?
Hint (a):
Multiply the cost by the number of gallons to determine what the cost would be.
Is the relationship between number of gallons and cost proportional? Explain.
Hint (b):
Refer to the Math Notes box in Lesson 1.1.2.
Answer (b):
Since the cost increases as the number of gallons purchased increases, the relationship between number of gallons and cost is proportional.
Gerald paid $$12.60$ for a tank of gas. How many gallons did he buy?
Hint (c):
This is the reverse of part (a). You know what the cost is, so divide the final price by the cost per gallon.

At right is a graph of this situation. Predict how the line would change to represent the average cost of gas in December of 2005, when gas cost $$2.20$ per gallon on average.
Answer (d):
The line would get steeper.

This graph is in the first quadrant. The x axis displays Gallons of gas. The y axis displays the Cost of gas in dollars. The graph is a straight line starting at (0, comma 0) going upward and passing through (8, comma 12).