I get confused when to use rather than or instead of....
I know rather than is used with verbs
instead of with nouns..

Can you shed more light with examples?

You are right to want to split hairs here, as there are often subtle differences in accepted usage of similar expressions. However, 'rather than' and 'instead of' are pretty much interchangeable. If there are any differences in their usage, then such differences will undoubtedly boil down to writers' personal preferences.

So, in short: don't worry about it. And if you see a 'split' between these two expressions in a multiple-choice problem, then the split is probably there to deflect your attention away from the splits that actually matter (those sneaky @(*%^@(&*'s!!)

If you want, you can read more on this web page about the usage of these phrases.

Let us have two things to do - A and B. And the Gmat asks us to use rather than or instead of in the sentence. In the sentence, we would use rather than if A has a distinct advantage over B. We will use instead of if it is just a matter of choice.
Let me explain:

A and B are equal...use instead of
A is superior to B...use rather than
I would have a orange instead of an apple.
I need vitamin C. Oranges have more vitamin C than apples do. I would rather have an orange than an apple.

Another example: The test results indicate that the chromosome Alpha rather than Beta is effective against tumor.
Instead of using chromosome Beta, we may use chromosome Alpha for treatment of tumor.

That's an interesting perspective on rather vs. instead. I guess the key is to find specific GMAT problems for which this distinction is made in this way. I cannot recall any, though I'd be curious to know. (To be clear, I'm not asking anyone to post the actual problems on this forum, as OG problems are a banned source. I assume, though, that referencing them by problem number is OK.)

Rey

nice one. thanks Ron.

Interesting discussion! Keys to remember for this test:

Both "X rather than Y" and "X instead of Y" will require parallelism for X and Y.

Instead OF begins a prepositional phrase, so Y will have to be in the form of a noun. Since parallelism is required, so will X.
Rather THAN can be followed by verbs or nouns - it's more flexible.

Solely as a result of that, "rather than" is more commonly right than "instead of" ON THE GMAT because there are more errors we can build into "instead of" options. If you have to guess, choose an option that uses "rather than." But, ideally, check the rest of the sentence (and don't forget about that parallelism issue!).

Note that this also means they won't give you two choices that are otherwise completely grammatically correct and use nouns for X and Y - and for which one uses "rather than" and the other uses "instead of." There'd be no way to choose - they'd both be right. (Yet another reason why "rather than" tends to be right on the GMAT more often than "instead of.")

Rey,

I had earlier written that comment as guest. I am now focusing on only RC this week, as that is my new weakness :? as per the practice exercises and the 1st test on MGMAT. After that, I am going to revisit OG11, and I am sure I will come across that question. This concept is in my homemade notes, so it has to be from OG11, MGMAT guide or from the Kaplan 2005 book.

For RC, I have exhausted techniques from MGMAT and Kaplan. At this stage, I feel that only way to improve is by extensive slogging! Practice...and practice. So that is what I am headed for. By far RC is my least favorite of all sections. I was able to improve SC from 40% to 90% using MGMAT SC guide, so I have faith in your techniques for RC too. I perhaps have a limitation on cleverness level, and to improve that, I have to work hard to train my mind. My progress tracker: http://d4dial.blogspot.com

Aragorn

I found another source on the web on this one which explains it by giving examples.....
http://prachi.sulekha.com/blog/post/2006/07/rather-than-vs-instead-of.htm

Rey,

After RC, I re-did CR questions from OG11. Rather than is used in CR Q100. As it is not SC, we cannot make it a GMat grmmer rule, but the context of the problem specifies situation X as having a distinct advantage over the situation Y in the question stem.

Today is the SC marathon day for me.....will redo all, and then take a break , and then give manhattan test 2! Id I find anything specific, I will post here.

A small question....re-did is incorrect. How to correct it?

My Gmat Progress Tracker: d4dial@blogspot.com

We've also found instances in RC and CR in which they break the grammar rules that they posit in the SC section! :)

Also, I think "redid" is not supposed to have a hyphen... though I think most people type it with the hyphen anyway...