Very good question gmatmadeeasy.
The basic principle that I follow is that the sentence must be able to communicate the meaning without any ambiguity. If after reading the sentence, I feel that there could be more than one possible meaning, then it is a good indicator that the sentence is not correct.
Nouns: "The people in my office are smarter than those in other offices."
Nouns : "The people in my office are smarter than those in other offices are."
Both the sentences are correct.
In the first sentence, the verb "are" is understood and hence has not been repeated. This is the preferred usage.
In the second sentence, the verb "are" has been explicitly mentioned and even though this is more wordy than the above, GMAT does not consider this as correct.
Actions: "Synthetic oils burn less efficiently than do natural oils."
Actions: "Synthetic oils burn less efficiently than natural oils."
Both the sentences are correct. GMAT may consider the first version to be more wordy than the second version, but this will not be the reason why GMAT will eliminate first choice.
The key thing to note is that in all the 4 sentences above, there is one and only one meaning possible. Hence there is no room for ambiguity.
Now consider the following sentence:
Tom is more afraid of dark than his wife.
Does it mean: Tom is more afraid of dark than his wife is.
Or does it mean: Tom is more afraid of dark than he is of his wife.
So in this scenario, you will need to change the sentence such that the meaning is absolutely clear.
To summarize, "meaning" is the key. When you state comparisons, make sure of these three things:
- Meaning must be absolutely clear.
The entities being compared must be grammatically and logically parallel.
Helping verbs may not be repeated if both verbs are supposed to be in same tense.
For e-GMAT users the above are covered in the following concepts:
