equation, and POE to get rid of any answer choices that are clearly on the wrong track. Then, it’s time to
plug some of your own numbers in to see what is going on in there.
Here’s an example:
7.
n = 1,273 – 4pThe equation above was used by the cafeteria in a large public high school to model the
relationship between the number of slices of pizza, n, sold daily and the price of a slice of
pizza, p, in dollars. What does the number 4 represent in this equation?
A) For every $4 the price of pizza decreases, the cafeteria sells 1 more slice of pizza.
B) For every dollar the price of pizza decreases, the cafeteria sells 4 more slices of
pizza.
C) For every $4 the price of pizza increases, the cafeteria sells 1 more slice of pizza.
D) For every dollar the price of pizza increases, the cafeteria sells 4 more slices of
pizza.Here’s How to Crack It
First, read the question very carefully, and use your pencil to label the variables. You know that p is the
price of pizza, and n is the number of slices, so you can add that information to the equation. If you can,
eliminate answer choices that don’t make sense. But what if you can’t eliminate anything, or you can
eliminate only an answer choice or two?
Even with everything labeled, this equation is difficult to decode, so it’s time to plug in! Try a few of your
own numbers in the equation, and you will get a much better understanding of what is happening.
Let’s try it out with p = 2. When you put 2 in for p, n = 1,273 – 4(2) or 1,265.
So, when p = 2, n = 1,265. In other words, at $2 a slice, the cafeteria sells 1,265 slices.
When p = 3, n = 1,261, so at $3 a slice, the cafeteria sells 1,261 slices.
When p = 4, n = 1,257, so at $4 a slice, the cafeteria sells 1,257 slices.
So now, let’s use POE. First of all, is the cafeteria selling more pizza as the price goes up? No, as the
price of pizza goes up, the cafeteria sells fewer slices of pizza. That means you can eliminate (C) and (D).
Choice (A) says that for every $4 the price goes down, the cafeteria sells 1 more slice of pizza. Does
your plugging in back that up? No. The cafeteria sells 8 more slices of pizza when the price drops from $4
to $2, so (A) is no good.
Now, let’s take a look at (B). Does the cafeteria sell 4 more slices of pizza for every dollar the price