CPM Homework Help : CC3 Problem 2-62

The graph below shows distances traveled by Car A and Car B. Car A is represented by the line containing point A, and Car B is represented by the line containing point B. Use the graph to answer the following questions.

A first quadrant graph where the x axis is time in hours and scaled from 0 to 4 and the y axis is Distance in miles scaled from 0 to 120. Line A starts at the origin going through the point (2, comma 120). Line B starts at the origin going through the point (4, comma 120).

Which car is traveling faster? How can you tell?
Hint (a):
Look at the slopes of the lines.
Answer (a):
Car A, because its line is steeper.
Find the coordinates of point A and point B.
Hint (b):
Look at the graph.
How fast did Car A travel (in miles per hour)? How fast did Car B travel?
Hint (c):
Speed is equal to distance divided by time.
Step (c):
$\text{Car A }= \frac{120}{2}; \text{ Car B }=\frac{120}{4}$
Answer (c):
$\text{Car A}=60\ \text{miles per hour}$
$\text{Car B}=30\ \text{miles per hour}$
Does the distance Car A has traveled vary directly with the time? Why or why not?
Answer (d):
Yes, because the graph of Car A is a straight line through the origin.