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# Manhattan SC

Author Message
Current Student
Joined: 11 Mar 2017
Posts: 45
Location: India
Schools: SMU '19 (A), LBS
GMAT 1: 670 Q48 V33
GPA: 3.3

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21 Mar 2018, 01:55
What is correct use of which is why and that is why in GMAT. Please help in the context of this sentence

That every worker has a clean criminal record is of some importance to investment banks which is why a stringent background check is a necessary prerequisite for all of their job applicants.
I searched the dictionary and found this explanation_:
Question
"That is why" and "which is why"
That is why and which is why can be similar in meaning but function in different ways in a sentence.

In that is why, that is a demonstrative pronoun.

In which is why, which is a relative pronoun.

That in that is why is usually the subject of a sentence or a clause that can stand alone:

I want to be involved in town government, and that is why I'm running for mayor.

My mother always gives me good advice, so that is why I need to ask her opinion.

His last movie was terrible, and I think that is why his career has stalled in recent years.

Which is why is used to introduce a subordinate clause (one that does not form a sentence by itself):

Motorcycles are dangerous, which is why we should wear helmets.

The company went bankrupt, which is why their new building is unfinished.

The sunsets here are beautiful, which is why many artists come to paint them.
Current Student
Joined: 11 Mar 2017
Posts: 45
Location: India
Schools: SMU '19 (A), LBS
GMAT 1: 670 Q48 V33
GPA: 3.3

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21 Mar 2018, 01:57
Manhattan Prep Instructor
Joined: 04 Dec 2015
Posts: 832
GMAT 1: 790 Q51 V49
GRE 1: Q170 V170

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23 Mar 2018, 08:39
1
Quote:
Which is why is used to introduce a subordinate clause (one that does not form a sentence by itself):

Motorcycles are dangerous, which is why we should wear helmets.

The company went bankrupt, which is why their new building is unfinished.

The sunsets here are beautiful, which is why many artists come to paint them.

On the GMAT, these examples are wrong.* 'Which' always stands in for a specific noun in the sentence. If you can't replace the 'which' with a specific noun in the sentence, and have it make sense, then it's wrong.

In your first sentence, 'dangerous' isn't a noun, so that doesn't work. 'Motorcycles' doesn't work either, because you can't say 'Motorcycles is why we should wear helmets.' It seems like the word 'which' should stand for something like 'the danger involved in motorcycling': 'The danger involved in motorcycling is why we should wear helmets.' But that isn't okay on the GMAT either, because the noun 'danger' isn't actually in the sentence. So, the first sentence is wrong: there's nothing there for 'which' to stand for.

On top of that, 'which' is a 'peanut butter word'. It usually refers to the noun that's closest to it. There are a very few exceptions, but generally, 'which' has to be very close to the noun it stands for. In your examples, 'which' is next to an adjective, not a noun.

*There's EXACTLY ONE official problem, in all the problems ever published, that goes against this rule. I still think it's a pretty useful rule!
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Re: Manhattan SC   [#permalink] 23 Mar 2018, 08:39
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