Suppose you have a cookie stand, and when you charge $3 per cookie box you sell 200 boxes. But when you raise your price to $4 you only sell 120 boxes. Write the equation for the number of boxes you sell as a function of the price you charge. Denote "b" for the number of boxes, and "p" for prices you charge, assume the function is linear.

Question

Suppose you have a cookie stand, and when you charge $3 per cookie box you sell 200 boxes.  But when you raise your price to $4 you only sell 120 boxes.  Write the equation for the number of boxes you sell as a function of the price you charge. Denote "b" for the number of boxes, and "p" for prices you charge, assume the function is linear.

Damon · Answer

b = k p + c where k and c are constants 200 = k (3) + c 120 = k (4) + c ------------------subtract 80 = -1 k so k = -80 back to first eqn 200 = -80(3) + c 200 = -240 + c c = 440 so b = -80 p + 440

Kirk · Answer

Thank you, I was stuck on this for several hours to how to write this out, thank you again!