The student council decided to purchase t-shirts for its members. Image Clothing quoted the following prices for the t-shirts. Which equation best describes the relationship between the total cost, c, and the number of t-shirts, t?

A. c = 9.00t
Incorrect. Find the slope to determine the cost of each t-shirt.

B. c = 5t + 20
Correct! The cost per t-shirt is $5. The company also charges an additional fee of $20.

C. c = 5t + 45
Incorrect. Find the y-intercept or the cost when t = 0.

D. c = 0.20t + 20
Incorrect. Find the slope to determine the cost of each t-shirt.

The table below shows various values for x and y.

Which equation best describes the relationship between x and y?

A. y = -3x + 10
Correct! The slope is -3 and the y-intercept is 10.

B. y = 3x + 4
Incorrect. Graph this line on your graphing calculator. Does it go through the points in the table?

C. y = - 1 3 x + 18
Incorrect. Graph this line on your graphing calculator. Does it go through the points in the table?

D. y = 1 3 x + 20
Incorrect. Graph this line on your graphing calculator. Does it go through the points in the table?

Which linear function best describes the graph shown below?

A. y = - 1 3 x + 2
Incorrect. This is an increasing line, so the slope must be positive.

B. y = 2x + 1 3
Incorrect. In a linear equation, y = mx + b, b is the y-intercept and m is the slope.

C. y = 3x + 2
Incorrect. Be sure you have calculated the slope correctly.

D. y = 1 3 x + 2
Correct! The slope is 1 3 and the y-intercept is 2.

To which of the following situations can the function y = 5x + 10 be used to describe?

A. Shannon is paid $10.00 per hour and earns $5.00 in tips each day. What is y, her earnings for working x hours?
Incorrect. In the equation, 5 is the slope and is being multiplied by x.

B. Brian bought a plant that is 10 inches tall and will grow 5 inches per month. What is y, the height of the plant after x months?
Correct! Since it grows at 5 inches per month, 5 must be multiplied by x and then added to 10.

C. The cost of renting a paddleboat is $5.00 per hour. What is y, the cost of renting the padding boat for x hours?
Incorrect. This would be correct if the constant 10 were not added at the end of the equation.

D. Tiffany rented 10 videos at a cost of $5.00 per video. What is y, the cost of renting x videos?
Incorrect. Examine the equation again. 5 is being multiplied by x (an unknown) not 10.

Christi graphed a linear function on her graphing calculator. Her graph is shown below.

Which of the following would produce a graph exactly like the one Christi graphed?

1. x	y
   -2	13
   -1	8
   0	3
   1	-2

2. y = 5x - 2
3. A student started with $2.00 and is spending $5 each week. What is y, the total amount of money spent after x weeks?
4. A student started with $2.00 and is saving at a rate of $5 each week. What is y, the amount of money saved after x weeks?

A.
Incorrect. Does the graph shown go through the points in this table?

B.
Incorrect. What is the y-intercept of the function shown in the graph?

C.
Incorrect. This description would result in a decreasing line.

D.
Correct! The y-intercept is 2 and since the line is increasing, it would represent a “saving” situation.