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SAT Math Traps to Avoid

With the highly publicized recent changes to the SAT scoring scale (which was expertly detailed by my colleague Brian Smith above), the opportunity cost of a single incorrect answer is at an all-time high. For comparison, an incorrect answer that could have cost you zero or, at most, ten points on your score in the past can now cost you up to thirty points if you are particularly unlucky. While most incorrect answers are due to the simple fact that the SAT can be really freaking hard at times, the ones that sting the most are the ones where you knew what to do conceptually but made an honest mistake. While students call these errors by different names (dumb mistakes, facepalms, score killers…), I only use one word to describe them: avoidable!

One of the best ways to avoid small mistakes is to know the types of questions in which the SAT employs traps to trick you, so I’ve channeled my inner Admiral Ackbar and identified two common SAT Math Traps and how to best avoid them:

The “Solve for X” Fallacy This is the simplest, yet most devastating, trap employed on the SAT. The premise is simple: students have been trained to solve problems for a single quantity or variable, usually x, since the very beginning of Algebra 1 and have not stopped doing so since. Solving for x is so ingrained in most student’s math DNA that they do it instinctively. Knowing this, the SAT will ask you to evaluate a simple equation not for the value x, but for a quantity involving x. Let’s look at a quick example: If 5x - 2 = 3x + 4, what is the value of 2x?

  1. -3
  2. -1
  3. 3
  4. 6

You have probably done problems like this a hundred times in your Algebra classes and dozens more in your test preparation and, as a result, will instinctually combine like terms and solve for x = 3. On a test in math class, you would circle that answer and move on. The SAT knows this, which is exactly why they ask for 2x instead! The correct answer is D, not C.

Beware of Graphs! Interpreting graphs is one of the core skills needed to succeed in the Calculator Math section of the SAT. There are two traps to look out for in questions involving graphs, all of which center around masking a graph’s scaling.

1. Different Scales of X and Y Axes — this is the most common trap used in questions involving graphs. A graph may increase by an order of 10 on the x-axis and by an order of 50 on the y-axis, for example. If you don’t look closely at both axes, you may make the mistake of assuming that they are constant on both axes, which can drastically affect your calculations for slope or other elements of an equation. They will also use gridlines to try and dupe you into thinking that the scale is the same for both axes!

Solution: No need to overthink this one. Just double check the scale of each axis!

2. “Phantom” Y- Intercepts — The SAT will ask you, on multiple occasions, to use a graph of a line to find that line’s equation. On a regular graph of the X-Y coordinate plane (i.e. a graph in which the x and y-axes intersect at the origin), the easiest thing to eliminate wrong answers is to use the graph to find the y-intercept. Testmakers knows this and will have the axes intersect at a point other than the origin to trap test takers into rushing to the wrong answer.

Solution: When finding intercepts, double check that the intersection point of the other axes has a value of 0!