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GMAT Sentence Corrections: Comparison

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.


Practice Questions

1) a question about Horace

2) a question about spiders


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10 Responses to GMAT Sentence Corrections: Comparison

  1. B.S. October 26, 2013 at 10:27 am #

    I was just thinking about this sentence in the article:

    “Again, not only is this allowed, but it’s also preferred, because in addition to correct grammar…”. If it were inserted the pronoun “it” after “not only”, would it make a better parallel sentence in GMAT standards?

    Great article by the way, thanks for posting!

    • Mike MᶜGarry
      Mike October 26, 2013 at 1:03 pm #

      Dear Bruno,
      Thank you for your kind words. —– That first clause already has a subject, the pronoun “this”, so inserting another pronoun would create a double-subject error. What comes after the word “not only” determines the rhetorical emphasis. If I begin with “Not only X is allowed, …” then the expectation is that I will make a contrast to another object, e.g. “… but Y is also allowed.” In the sentence you cited, I didn’t want to create a contrast between two different nouns, but between two different verbs. That’s why the auxiliary verb “is” had to come right after the words “not only”. Does all this make sense?
      Mike 🙂

  2. rashmi June 19, 2013 at 11:24 am #

    Comparable in tensile strength, spider’s silk is much better than high-grade alloy steel at holding its own weight, considerably lighter because the organic composition is less dense than the metallic elements.

    In this sentence, “its” is referring to what: spider silk or high-grade alloy steel?

    • Mike MᶜGarry
      Mike June 19, 2013 at 12:16 pm #

      Well, in a way, we could say the word “its” is referring to both of them. You see, in parallel, and in comparisons which are a special case of parallelism, we can drop repeated phrases. The full long awkward version would be —
      “…. spider’s silk is much better at holding its own weight than high-grade alloy steel is at holding its own weight …” Obviously, that’s a nightmare that never would be correct on the GMAT, but that version makes clear which “its” refers to which item. When we don’t repeat the phrase, in a way, it applies equally to both of them.
      Does this make sense?
      Mike 🙂

  3. Confuse Mind August 17, 2012 at 4:43 am #

    If you combine rule 1 and rule 3 above, we can arrive at a sentence in which actions are compared and thus ‘as’ is used but repetition of action is omitted because it is just a repetition.

    Will such a sentence be correct on GMAT?

    Ram plays cricket as Shyam does – correct
    Ram plays cricket as Shyam – correct y/n

    • Mike MᶜGarry
      Mike August 17, 2012 at 4:42 pm #

      Intended meaning matters here.
      If I merely want to indicate that Ram plays cricket and, coincidentally, so does Shyam, then I would say:
      “Ram plays cricket as Shyam does”, or
      “Ram plays cricket as does Shyam”
      BUT, if I wish to emphasize that Ram’s style of play is very much like Shyam’s style of play, I would say
      “Ram plays cricket like Shyam.”
      “He runs like Jesse Owens.”
      “He sings like an angel.” etc.
      There, the comparison is between nouns.
      Mike 🙂

  4. Confuse Mind August 17, 2012 at 4:40 am #

    Which of the following is correct?

    Ram plays as good cricket as Shyam.
    Ram plays as good cricket as Shyam plays.

    Is plays in the second essential?
    As per the rule-3 mentioned above, can it be avoided as it is just a repetition.

    • Mike MᶜGarry
      Mike August 17, 2012 at 4:32 pm #

      Yes, it’s best to avoid the repeated word, as long as omitting it introduces no ambiguity.
      Mike 🙂

  5. Confuse Mind August 17, 2012 at 4:26 am #

    Which is correct?

    The United States has more debt than does China.
    The United States has more debt than has China.

    • Mike MᶜGarry
      Mike August 17, 2012 at 4:31 pm #

      The US has more debt than does China. = correct
      The US has more debt than China has. = correct, but sounds wordy
      The US has more debt than China. = unambiguous, so also correct — in fact, probably the best of the three, because it’s most concise.
      Mike 🙂

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