Which of the following graphs is a model of inverse variation with a domain of x > 0?

A.

B.

C.

D.

A.
Incorrect. This is a model of direct variation.

B.
Incorrect. This is a quadratic model.

C.
Incorrect. This is a model of direct variation.

D.
Correct! The graph would be positioned in the first quadrant.

The volume of a gas varies inversely with the pressure. A graph of the relationship is shown below. What is the pressure of the gas when the volume is 125 cubic inches?

A. 50 pounds
Incorrect. Find x when the value of y = 125.

B. 2 pounds
Correct! x = 2 when y = 125.

C. 5 pounds
Incorrect. Find x when the value of y = 125.

D. 8 pounds
Incorrect. Find x when the value of y = 125.

The following graph describes an inverse variation. What is the value of k?

A. 5           B. 1 5           C. 1           D. 2

A.
Correct! xy = k for all ordered pairs.

B.
Incorrect. Remember, xy = k for all ordered pairs.

C.
Incorrect. Remember, xy = k for all ordered pairs.

D.
Incorrect. Remember, xy = k for all ordered pairs.

The student council is planning a bus trip to the Houston Museum of Natural Science. A graph describing the relationship between the number of students that go and the cost per person is shown below. What would the cost per person be if 20 students go to the museum?

A. $50
Incorrect. Find the value of y when x = 20.

B. $25
Incorrect. Find the value of y when x = 20.

C. $60
Incorrect. Find the value of y when x = 20.

D. $35
Correct! When x = 20, y = 35.