Brian Galvin is the Director of Academic Programs at Veritas Prep, where he oversees all of the company's GMAT preparation courses.
On the GMAT, Data Sufficiency questions can often be tricky or confusing simply because of the unique format of the question. It is rare, if it occurs at all, that you encounter situations in which you are not asked to solve a problem, but are asked if the tools provided would be sufficient to do so.
To gain experience with the tricks and traps that the format allows the writers of the exam to employ, you can try writing a few questions of your own with the intent of 'tricking and trapping' your friends. (In order to do so, you will need to anticipate the mistakes that someone could easily make -- and those are the mistakes that could trip you up, too. Does it seem as though someone could forget about the exception to the rule that you "hid" in statement 1? Does statement 2 supply that one missing piece of information that was omitted from statement 1, tempting someone to select "B", even though statement 2 is clearly insufficient on its own? Laying these mental traps for someone else is a great way to become more aware of them for yourself. (And knowing is half the battle!)
Note that you can create questions in this format even without using any math. Even without math, many of the same traps apply:
Question: Name this U.S. President.
(1) He has the same first name as his father.
(2) His presidency began after the American Civil War.
You may be tempted to select (C), narrowing the choices down to John Quincy Adams and George W. Bush, then eliminating Adams with statement 2. However, doing so would assume that the father mentioned in statement 1 was also a President, which is not explicitly stated. Actually, the answer must be (E), as both George W. Bush and William McKinley, for example, had the same names as their fathers -- McKinley's father was not a President, but that wasn't required by this question, even though some may have assumed it.
That assumption error is akin to a GMAT examinee assuming that a value must be an integer, or must be a positive number. By writing trivia questions designed to capitalize on potential errors, you can become more attuned to the mistakes that you may make on test day.
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