The GMAT Sentence Correction will ask you about several sentences involving comparisons. Why? Because, in the business world, people compare things all the time. Microsoft is a bigger company than Apple. The United States has more debt than does China. Caterpillar’s stock, like DuPont’s, pays a dividend. Nobody else put a hybrid on the market as fast as Toyota did. The economics you will study later; right now, do you understand the grammar of the following four sentences?
Crucial Comparison Idea #1: “like” vs. “as”
The word “like” is a preposition. That means it can be followed only by a noun, not a whole phrase. That means, “like” is useful for comparing nouns, but not useful for comparing actions. Correct: “Joey, like me, plays baseball.” (comparing two nouns, Joey & me.) Incorrect: “I enjoy playing baseball, like Joey does.” (comparing two actions).
To compare actions, we need the word “as”. The word “as” is a subordinating conjunction, which is a fancy ways of saying it is followed by full noun + verb phrase. Thus: Correct: “I enjoy playing baseball, as Joey does.” Comparisons of actions require the word “as.” The GMAT loves to ask about this.
Crucial Comparison Idea #2: Parallelism
When comparing verbs or complex phrases, each element is in parallel to the others, and thus must have the same grammatical form. Consider the following hypothetical prompt to a GMAT Sentence Correction question:
Beethoven preferred to expand the development section of sonata form, exploring the limits of rhythmic and harmonic variation of the theme, rather than constructing the more symmetric sonata forms of Mozart.
Did you spot the grammar mistake? It’s a mistake of parallelism, but as is typical for the GMAT, it’s hard to spot because of all the extra words. Fundamentally, the comparison is about two verbs, and Beethoven prefers one rather than the other. Verb #1: “to expand”, an infinitive. Verb #2: “constructing”, a participle. These are not in the same grammatical form. Correcting this sentence would involve making both of them infinitives — “to expand . . . to construct” — or both participles — “expanding . . . constructing.”
Crucial Comparison Idea #3: Missing Words
Consider this sentence:
Lamarck’s idea of how inherited traits accumulated over several generations of a species was not as sophisticated as modern genetics’ idea of how inherited traits accumulated over several generations of a species.
Yes, that is an atrocious sentence, far too wordy and awkward. Consider this revision:
Lamarck’s idea of how inherited traits accumulated over several generations of a species was not as sophisticated as modern genetics’ idea.
That conveys all the information, without repeating the same words, which are obvious from context. Not only is this 100% grammatically correct, but because it’s shorter and more elegant, it will always be preferable on GMAT Sentence Correction.
In comparison of complex ideas, as long as all present elements are correctly in parallel, you can omit repetition of the words that will be obvious from context. “My car is faster than Henry’s.” That is a 100% correct sentence: the word “car” following “Henry’s” is clearly implied, so it need not be stated explicitly. Again, not only is this allowed, but it’s also preferred, because in addition to correct grammar, the GMAT Sentence Corrections are about concision: what is the shortest way to say something so that it is still grammatically correct and unambiguous? Concision is one of the pillars of GMAT Sentence Correction, and omitting the needless repetition of words in comparisons is one of the test-makers’ favorite tricks.
If you master these three crucial ideas, you will be knocking out GMAT Sentence Correction comparisons faster than nobody’s business.