You obviously don’t need to memorize these for the GMAT (A house divided against itself is not an integer), however some expressions can be easily applied to various GMAT problems. One common expression is that you’re comparing apples and oranges. This expression typically means that you are attempting to compare two elements that are not analogous and therefore incomparable. This idiom can be particularly apt in sentence correction problems.

When looking over Sentence Correction GMAT questions, there are common errors that appear over and over as potential gaffes that must be avoided in the correct answer. One such error is that of the false comparison, where the author erroneously compares one thing to another of a different type. Consider the frequently misused example of “The Yankees’ record is more impressive than the Mets.” Without adding a possessive determiner (Mets‘) at the end of the sentence, we are comparing the Yankees’ record with the actual Mets team. This is clearly an illogical comparison, yet one that often goes unnoticed.

Some questions will contain more than a simple comparison issue, and the other rules of English grammar we know must also be followed, but comparison issues tend to disproportionally mess students up. These errors frequently occur in daily life without anyone batting an eyelash, so they’re often difficult to spot.

Let’s look at an example that highlights this issue:

Unlike the terms served by Grover Cleveland, separated by four years, all former two-term U.S. Presidents have served consecutive terms.

(A) Unlike the terms served by Grover Cleveland, separated by four years

(B) Besides the terms of Grover Cleveland that were separated by four years

(C) Except for Grover Cleveland, whose terms were separated by four years

(D) Aside from the terms of Grover Cleveland that were separated by four years

(E) Other than the separated terms of Grover Cleveland, of four years

Many amateur historians will stop to consider the accuracy of the subject matter, more astute GMAT students will quickly recognize that the original sentence contains a comparison trigger word. The word “unlike” typically signals that we’ll be comparing two or more elements; however these elements may or may not be congruent. If they are not comparable, we’ll be dealing with a glaring comparison error. This may not be the only error we have to sort through, but it’s undeniably a good place to begin our analysis.

The sentence begins by comparing the terms of the 22nd (and 24th) U.S. president to the other 11 presidents who have served two presidential terms. This connection should immediately seem incorrect, as presidential terms and people are not interchangeable. The underlined portion will thus need to be changed as the second half of the comparison is not underlined and therefore must remain untouched. Answer choice A can be eliminated because of this comparison mistake.

Looking through the other choices, answer choice B changes a couple of words in the answer choice, but still starts by comparing terms to humans. It can therefore be eliminated. Answer choice C changes the wording to begin with “Except for Grover Cleveland, whose terms…”, which changes the comparison to one person versus other people. This comparison is logical and acceptable, and the rest of the sentence seems fine as well. We can eliminate answer choices A and B so far, but not answer choice C. Let’s look at the two remaining choices before we look for another error.

Answer choice D again tries to compare terms to a person, which can easily be eliminated. Answer choice E makes the same mistake, and this sentence makes more mistakes as we read through all of it, however one strike is all you get on the GMAT. Only answer choice C correctly compares the 24th (and 22nd) U.S. president to the other presidents. Answer choices A, B, D and E are all eliminated because of the same comparison error, and choice C must be the correct answer.

Sentence Correction on the GMAT is full of questions like this, where one issue will get you to the correct answer, but if you don’t see it, you’ll spend time dissecting slight meaning differences between synonyms. If you don’t recognize the comparison error, you might think that this question is asking you to choose between “Aside” and “Unlike” in a sentence, which is a fool’s errand. Recognizing the common errors that pop up on the GMAT helps both your success rate and your pace, helping build confidence. Best of all, it ensures you’re comparing apples with apples.

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