A bicycle tire is pumped to a pressure of 120 psi (pounds per square inch). While riding his bike, Daniel ran over a small nail, and the tire has a small hole in it. Air is leaking and the tire is losing pressure at a rate of 12 psi per minute. If you graphed the pressure of the tire as the output, compared to the number of minutes as the input, which of the following statements about the graph would not be true?
A.
The graph would be a line.

Question

A bicycle tire is pumped to a pressure of 120 psi (pounds per square inch). While riding his bike, Daniel ran over a small nail, and the tire has a small hole in it. Air is leaking and the tire is losing pressure at a rate of 12 psi per minute. If you graphed the pressure of the tire as the output, compared to the number of minutes as the input, which of the following statements about the graph would not be true?
A.
The graph would be a line.

anonymous · Answer

B.
The graph would rise from left to right.     
C.
The graph would be only in the first quadrant.
D.
The more time has passed, the lower the psi would be.

anonymous · Answer

Let's call the pressure in the tire 'P' and the number of minutes since he rain over the nail 'm'. We know that P=120 when m=0. We also know that for eveyr increase of m by 1, P drops by 12. This gives us the equation $$P=120-12m$$

We can graph this to get our answer:
|dw:1391804091983:dw|

Now check each choice one by one to find the one that is not true. If you do that you wil lsee that the answer is (B).