Think Like a Test Maker And Avoid Trap Answers on the SAT and ACT
The Princeton Review
Partial Answer Script
The makers of the SAT and the ACT have been at it for a while. They are well aware of
the best ways to get students to fall for tricky-trap answers. One of the most common
methods they use on the Math sections is that of the partial answer. But once you know what
to look for, you’ll be too savvy to fall for that!
Let’s look at some examples so you’ll be able to recognize a partial answer when
you encounter one.
The first comes from the SAT. Here’s the question:
If x is directly proportional to y squared and x = ½ when y = 1/3, what is the positive
value of y when x = 2?
Since we’re focused on the trap here and not the actual math content, let’s work
through the problem together.
First, you’ll set up an equation that looks something like this:
x/y2 = x/y2
From there, you’ll take what you know from the problem and plug it in:
(½)/(1/9) = 2/y2
We know that x is equal to ½ when y is equal to 1/3. However, we have 1/9 in the denominator
because our equation calls for y squared, not just y. That’s how we decide what goes
on the left of our equation. This y-squared bit will be important later, so keep it at
the front of your brain!
Our next step is to simply solve the problem. We’ll start by cross-multiplying ½ times
y2 and 1/9 times 2, which simplifies to 2/9.
(½)y2 = 2/9
From there we need to isolate the variable y, so multiply both sides by 2. That’ll
bring us to:
y2 = 4/9
Now, an eagle-eyed student like you will probably point out that our work here is not finished,
so let’s go back to the question the test asked:
If x is directly proportional to y squared and x = ½ when y = 1/3, what is the positive
value of y when x = 2?
Based on that question, are we solving for y2 or are we solving for y? The answer is
plain old y. However, I can guarantee you that 4/9 will be one of the four answer choices
on the test. That’s the trap answer. The test makers count on you moving as quickly
as possible through the test, so they expect that once you recognize an answer among your
choices, you’re going to choose it and keep it moving through the rest of the section.
Do. Not. Fall for it.
Let’s finish up by going back to the problem where we left off:
y2 = 4/9
Our last step is to calculate the square root of 4/9, which gives us:
y = 2/3
Once you’re there, look for that among the answer choices. It’ll be there right alongside
4/9, but it’ll be a much better choice in the long run—it’ll be the RIGHT choice.
Trust me when I say the extra time it takes to double-check what the question is asking
against the answer you’ve gotten is worth it—it may just be the difference between
snagging a point you’ve already done the work for, or of losing that point.
Let’s take another example, this time from the ACT:
If given a trapezoid with the following dimensions in inches, what is the area in square inches?
Let’s pretend for a second we don’t know the formula for the area of a trapezoid, instead
dividing the figure into two separate shapes: a triangle and a rectangle.
The dimensions of the rectangle are 5 by 2, which gives an area of 10. Any guesses where
this is going? If you guessed “trap,” you’ve got the right idea!
The test makers are absolutely counting on you forgetting to add in the area of the triangle,
which is why they’re almost guaranteed to offer 10 as one of the answer choices. The
partial answer strikes again, unless you take the time to double-check that you’ve answered
the question the test is asking.
Going back to the figure, you’ll need to calculate the area of the triangle—3—and
add that to the area of the rectangle. That means the correct answer is 13. The trap here
makes an otherwise fairly simple question into one that can be a bit tricky.
Make sure you focus part of your test prep on recognizing the ways in which the test
makers try to trick you so you don’t miss out on any points you rightfully deserve on
the SAT or ACT.
Don’t fall for those trap answers. If you can do the hard part—the math itself—then
you can definitely do the easy part—which is simply re-reading the question to ensure
you’re answering what’s being asked. So do it. Every time. And get points for your
knowledge and hard work.
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