Junkfood Jill spends all of her income on jellybeans and cola. Suppose that Jill's income is $30, the price of a bag of jellybeans is $6, and the price of a bottle of cola is $2. If bags of jellybeans are graphed along the vertical axis and bottles of cola are graphed along the horizontal axis, what is the slope of the budget line?

Question

Quizplus · Accepted Answer

The equation for the budget line is: 
6J + 2C = 30, where J is the number of bags of jellybeans and C is the number of bottles of cola.

We can solve for C: 
2C = 30 - 6J 
C = 15 - 3J

Now we can plot this on a graph with J on the vertical axis and C on the horizontal axis:

|        /
  |     /     
J |  /        
  |______________
     0   5   10

The intercept on the horizontal axis is 15 (when J = 0), and the slope is -3 (since every extra bag of jellybeans means 3 less bottles of cola in the budget). Therefore, the answer is D, with a slope of -1/3.

Junkfood Jill Spends All of Her Income on Jellybeans and Cola