The rate at which a plant grows is constant. At the 3rd week it is 12 inches tall and at the 5th week it is 20 inches tall. If this information is plotted on a coordinate plane, what is the y-coordinate of the the point (1, y)?
A) 1
B) 2
C) 4
D) 9

C) 4. Explanation: Since the rate is constant, you can find the y coordinate by simplifying the given coordinates. Image that the graph is (week, height), which means that the given points are (3, 12) and (5, 20). Put these into a fraction, and simplify them to get x as 1. y/x = 12/3 = 4, and 20/5 = 4. Since the rates are consistent with 4 when simplified to get the x variable to 1, that means that the y coordinate of (1, y) is 4.