1. The graph shows a proportional relationship between a family's distance from home, y, and the time they spend driving, x. Write an equation for the relationship shown by the graph.
2. Michael is having a yard sale. For each item, he is asking for nine-tenths of the price for which he bought the item. Write an equation for the situation, where y is the price he is asking and x is the original price of the item.
3. The pressure exerted by a certain liquid at a given point varies directly as the depth of the point beneath the surface of the liquid. The pressure at 60 feet is 420 pounds per square inch. What is the pressure at 20 feet?
4. Writing The graph shows a proportional relationship between the variables y and x.
a. Write an equation to model the relationship.
b. Explain how you know there is a proportional relationship if you are given either an equation or a graph.
5. Think About the Process The graph shows a proportional relationship between y and x.
a. Find the value of the constant of proportionality m.
b. Write an equation that models the line.
6. Money The graph shows a proportional relationship between a person's total savings in dollars and the number of weeks they have been saving. Write an equation that models the savings.
7. Write an equation for the following proportional relationship. y is one-eleventh of x.
8. Suppose y varies directly with x, where y = 9 when x = 8.
a. Write a direct variation equation that relates x and y.
b. Find the value of y when x = 16.
9. If x varies directly as y, and x = 6 when y = 2, find x when y = 4.