First, some practice questions.
1) Snakes molt their skins regularly, for the purpose of regenerating skin worn by ground contact and for eliminating parasites, like ticks and mites, and this made ancient people venerate the snake as a symbol of resilience and healing.
(A) for the purpose of regenerating skin worn by ground contact and for eliminating parasites, like ticks and mites, and this made ancient people venerate
(B) for regenerating skin worn by ground contact and for the purpose of eliminating parasites, such as ticks and mites, causing ancient people to venerate
(C) so as to regenerate skin worn by ground contact and to eliminate parasites, such as ticks and mites, and these shed snake skins made ancient people venerate
(D) in order to regenerate skin worn by ground contact and for the purpose of eliminating parasites, such as ticks and mites, with ancient people venerating
(E) to regenerate skin worn by ground contact and to eliminate parasites, like ticks and mites, and these cause ancient people to venerate
2) In the spring of 1778, the Continental Army installed a “great chain” across the Hudson River, at West Point, in order to prevent British ships to navigate into the vulnerable regions to the north.
(A) in order to prevent British ships to navigate into
(B) by preventing British ships from navigating into
(C) so that they prevented British ships to navigate to
(D) to prevent British ships from navigating to
(E) by means of preventing British ships from navigating to
3) The CEO of Laminar Flow gave his R & D team a new $300 million dollar research facility, with cutting-edge technology, that they can research potentially revolutionary innovations in.
(A) that they can research potentially revolutionary innovations in
(B) for conducting research about revolutionarily potential innovations
(C) that can be the place for them to research potentially revolutionary innovations
(D) where it would be conducting research into revolutionary potential innovations
(E) in which to conduct research into potentially revolutionary innovations
Infinitives
The infinitive is the “main form” of a verb. It’s the standard form of a verb listed in a dictionary. The infinitive form of a verb is identical to the present tense for that verb, except for the verb “to be.” An infinitive = “to” + [infinitive form]. An infinitive often acts as a noun, and may be the subject of a sentence.
Infinitives often appear on the GMAT at the beginning of infinitive phrases. Some verbs idiomatically take an infinitive, and this is a common reason why an infinitive appears in a GMAT sentence.
Infinitives of Purpose
The infinitive of purpose is another very common reason why an infinitive would appear in a GMAT sentence. Unlike the aforementioned situation, in which only specific verbs idiomatically call for the infinitive, the infinitive of purpose can be used with any verb. The infinitive of purpose expresses the reason for the main verb, the goal of the action of the main verb.
4) She visited Paris to see her former roommate.
5) He bought the new car to impress his girlfriend.
6) After World War II, the Soviet Union absorbed Eastern Europe into the Warsaw Pact, to protect itself from any more invasions.
7) Last October, Legacy Productions sold its East Asian divisions, to raise cash for its aggressive new research projects.
First of all, notice that this purpose, this goal, has to be expressed as an infinitive. Any construction of the form [preposition] + [gerund] will not be an appropriate substitute.
Variants
The standard form of the infinitive of purpose is simply an infinitive, “to do X“, that follows the verb and any object of the verb. Two variants are “in order to do X” and “so as to do X.” Both of these allow for some clarity: if there are multiple infinitives, or even multiply prepositional phrase beginning with “to”, then either of these phrase would make the presence of the infinitive of purpose more clear.
8a) He was no longer able to go to New York to see the international art exhibitions.
The word “to” appears several times in that sentence: once in an infinitive idiomatically accompanying the word “able”, once in an ordinary prepositional phrase, and once in an infinitive of purpose. While it’s not strictly necessary, we can add a little more clarity to that sentence with the construction:
8b) He was no longer able to go to New York in order to see the international art exhibitions.
In this construction, it’s very clear which “to” phrase is the infinitive of purpose.
The construct “so as to” has already been discussed as an idiom of consequence. This is considerably more formal, and therefore quite likely to appear in the GMAT Sentence Correction.
Summary
In your outside-of-the-GMAT reading, notice the infinitive of purpose. This accounts for a large number of the infinitives used in formal writing. Identifying this piece is crucial for understanding the logic of a sentence, and logic is the most underestimated factor in GMAT Sentence Correction. Here’s an additional practice question from inside the Magoosh product.
9) http://gmat.magoosh.com/questions/3217
If you have any questions about what we discussed, please let us know in the comment section.
Explanations to the practice questions
1) Split #1: listing examples. On the GMAT, it is forbidden to begin a list of examples with “like.” We need to use the idiom “such as.” In discussing the parasites, choices (A) & (E) make the mistake of using “like ticks and mites,” so these two are incorrect.
Split #2: the phrase “for the purpose of doing X” is a long wordy way to express purpose. It is grammatically & idiomatically correct, but probably a bit too wordy to be correct on the GMAT. Here, in both appearances, it is put in parallel with an ordinary “for” + [gerund] construction, which is never appropriate for showing purpose. Choice (A) has “for eliminating” and choice (B) has “for regenerating,” so both of these are incorrect.
After these two splits, we are left with (C) & (D). Choice (D) makes the questionable choice of putting an “in order to” phrase in parallel with a “for the purpose of” phrase; this is certainly wordy, and may be considered logically incorrect on the GMAT. The structure “with” + [gerund] in the second half of (D) is always incorrect on the GMAT. This combination is enough to eliminate (D).
By contrast, choice (C) has the elegant structure of two infinitives in parallel after the “so as” structure, and the second half is logical clear. Choice (C) is the best answer here.
2) Split #1: idiom. The verb “prevent” idiomatically takes the preposition “from.” Choices (A) & (C) make the mistake of following “prevent” with an infinitive phrase, which is idiomatically incorrect. We can reject those two choices.
Split #2: navigating “to” vs. “into” the northern regions. The choice of “into” is a little unusual, but it’s not incorrect. We cannot reject anything on the basis of this split.
Split #3: cause vs. consequence. The remaining choices present logical difficulties. Consider the two actions:
(1) installing the “great chain” across the Hudson
(2) preventing the ships from navigating
What causes what? Which is the cause and which is the purpose? Clearly, (1) is the cause, the purpose of doing (1) is to accomplish (2); in other words, (2) is the goal. Thus, using an infinitive of purpose for (2) would be appropriate, and that’s exactly what (D) does. Both (B) & (E) suggest that (2) is the cause or means, and that (1) is the purpose or result, and this does not make sense. Both of those are incorrect.
Choice (D) is the only possible answer.
3) Split #1: Pronoun agreement. The “R & D team” is a collective noun: it may have many members, but as a noun, it is singular, and it requires a singular pronoun. Choices (A) & (C) use the plural pronoun, so they are incorrect.
Let’s look at each answer individually.
Choice (A) is wrong because of the pronoun problem. Notice that it also ends a sentence in a preposition. Ending a sentence with a preposition was once considered completely wrong: it’s now in more of a grey zone, but I have only seen it appear as part of incorrect answer choices on the GMAT SC. This is incorrect.
Choice (B) is wrong because it uses the “for” + [gerund] structure in place of an infinitive of purpose. Also, the phrase “revolutionarily potential” changes the meaning from the original. This is incorrect.
Choice (C) has the extremely awkward & wordy “that can be the place for them to ..” as well as the pronoun mistake. This is incorrect.
Choice (D) has an extremely strange tense, the conditional progressive. There is no reason for the tense to be conditional, hypothetical, and there is no reason for the tense to be progressive, happening right at this instant. Because of the problems with verb tense, this is incorrect.
Choice (E) uses the elegant “in which” structure to avoid ending with a preposition, and it correctly uses the infinitive of purpose. This choice is sophisticated and completely correct grammatically. This is the best answer.
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