Hi gmatmachoman,
Since the topic is titled.... USAGE OF LIKE v/s AS v/s SUCH AS, i thought you might be interested in an excerpt from sumit's gmat verbal notes.
Like vs As
First of all, I should say that just about any GMAT grammar rule will have some exception. For this reason, I prefer not to refer to "English grammar rules" but to "GMAT patterns." As I'm sure you're aware, it's very difficult to give a pattern that applies in every case. I would say that generally speaking, your summary is good, but just to be sure, I want to restate:
Use like when you want to focus on two nouns;
Use as when you want to focus on two nouns doing two actions.
Another little trick is that "just as" can replace "in the same way that..."
Let's compare two very similar sentences that could cause confusion:
My Siamese cat moved across the floor just like a lion stalking its prey.
To me, this sentence stresses how two different cats are similar. I know this is confusing because we have a noun, "lion" and a participle "stalking," which would seem to indicate that we should use "as," but it's just not so. In this sentence, do you think we're tying to say
My Siamese cat moved across the floor in the way that a lion stalks its prey.
I don't think so...
My Siamese cat moved across the floor just as a lion stalks its prey.
This one sounds bad to me, I think because we are not explaining how the cat is moving. Furthermore, at some point, we are going to run into some ambiguity--"as" does also mean "at the same time," and I also think that the sentence above does sound a bit like two things are happening at the same time.
Let's look at a better sentence:
My Siamese cat moved across the floor just as a lion stalking its prey moves.
This one sounds very good to me; it explains how a my cat moved.
Furthermore, it has the same meaning as:
My Siamese cat moved across the floor in the way that a lion stalking its prey moves.
Like vs. Such As
Question: What's the difference between like and such as?
Example of the "mistake" that we make in everyday speech: Can you buy me some fruit like oranges or grapefruit?
How the GMAT Official Guide would explain this mistake: Using like in this answer choice mistakenly suggests that the utterer of the request does in fact not want oranges or grapefruit, but rather some other kind of fruit that is similar to oranges or grapefruit.
In normal English: In GMATLand, like means similar to, and such as means for example. Take a look at these examples:
"¢ Can you buy me some fruit like oranges or grapefruit?
In GMATLand, this sentence would mean that you do NOT want oranges or grapefruit; instead, you'd prefer some fruit similar to oranges and grapefruit. For example, you may want pomelo, lemons, or limes. Yes, I know this sounds a little crazy, but our goal is to understand what GMAT is looking for, not what is "correct" English.
"¢ Can you buy me some fruit such as oranges or grapefruit?
Yes, this is what we're supposed to say in GMATLand -- oranges and grapefruit are examples of the type of fruit we want.
"¢ I would like you to buy such fruit as oranges and grapefruit for me, if you don't mind.
This is simply a variation -- notice how such and as are separated. Separating the two elements tends to make this pattern a bit harder to see.
