Comparisons - This is how you crack 'em.. (Part 1)

Learn this, 'cos the GMAT loves to test you on comparing stuff. 


Comparisons either compare two parts of a sentence and occasionally more. It is important to first know the signal words or phrases of comparisons. The next step is to identify the parts of the sentence being compared to one another. Finally, ensure that the two parts of the sentence being compared are truly parallel, both structurally and logically. The most common comparison words are like, unlike, as and than. The others are listed below:
Comparison Signal words:
like - as
unlike - as (adj.) as
more than - as much as
less than - as little as
faster than - as fast as
different from - the same as


"Like" vs. "As"
Possibly the most common words, you need to know to distinguish between the two.

• Like is a preposition and is therefore followed by nouns, pronouns and noun phrases. Never put a prepositional phrase after like. A clause contains a working verb, which can be the main verb in the sentence.
• You can correctly use Like to compare two nouns.

Example:
CORRECT: Like her brother, Shruthi aced the GMAT.

• Like is followed by the noun phrase her brother. The entire phrase Like her brother indicates a comparison between Ava and her brother. 
• Like can also be followed by a gerund (-ing words). 

Example:
CORRECT: Like swimming, jogging is great exercise.

• Contrarily, As can appear either as a preposition (appearing with a noun) or a conjunction (appearing with a clause).
• You can correctly use As to compare two clauses. 
• You CANNOT use like to compare two clauses.

Examples:

INCORRECT: LIKE her brother DID, Ava aced the test.

CORRECT: AS her brother DID, Ava aced the test.

• As Ava did is a clause, with DID as a working verb. Therefore, you must use As to make the comparison between her brother DID and Ava aced the test.
• It is common to use like to compare in speech, but it is always wrong in writing.

Keeping Comparisons Parallel

1. Comparisons must ALWAYS be logically parallel. That is, they must compare similar things.

Example: Frank's build, LIKE his brother, is broad and muscular

Here, Frank's build is being compared to his brother directly, which would not make sense. 

CORRECT: Frank's build, LIKE his brother's, is broad and muscular.

• Notice that the word build isn't repeated, it is implied.
• You may also use the word that instead of build. It will also imply build.

CORRECT: Frank's build, LIKE that of his brother, is broad and muscular.

• Note that if the noun were plural, you would use those.

Example: Frank's toes, LIKE those of his brother, are short and pink.

• Finally, you can shift the last word in the noun phrase and rephrase the sentence.

Example: Frank, LIKE his brother, has a broad and muscular build.

 If necessary, refer to page 122 for a harder example.

1. Comparisons must be structurally logical - They must have the same grammatical structure.

Example:

INCORRECT: I like to run through forests more than I enjoy walking through crowds.

This statement is incorrect because run through the forests is not parallel with walking through crowds. To correct this statement, make both grammatically parallel.

CORRECT: I like running through forests more than I enjoy walking through crowds.

Omitting Words

• It is possible to omit words from the second part of a comparison if it does not sound ambiguous.

Examples:
CORRECT: 
My toes are longer than Brian's [toes]
My toes are longer than the Smiths' [toes]


My car is bigger than Brian's [car]

My car is bigger than the Smiths' [car]

• Notice that the possessing noun (Brian, the Smiths') can be plural or singular irrespective whether the possessed noun is plural or singular.
• Any singular-plural combination is possible as long as it makes logical sense.
• You may also eliminate units, verbs and whole clauses from the second part of the sentence

CORRECT: 

Whereas I drink 2 quarts of milk a day, my friend drinks 3 [quarts of milk]

I walk faster than Brian [walks]

I walk faster now as [I walked] when I was just discharged from surgery.

• Remember only to add helping verbs such as do, be and have.

Example:

INCORRECT: Vishal eats more carrots than donuts.

CORRECT: Vishal eats more carrots than he does donuts.

• You invariably need a helping verb to resolve the role of the second part of the comparison. (Refer for example)
• The GMAT also sometime allows extra helping verbs

Comparative and Superlative