Beat The GMAT a GMAT & MBA community

Hi, there. I'm happy to give my two cents on this.

As you are finding, there can be a big difference between (a) knowing math, and (b) being successful on GMAT math. In addition to all the math concepts with which you are no doubt familiar, you also need to know strategy for interpreting and solving the questions. Data Sufficiency in particular is very challenging because, for most folks, it's unlike any previous math problem they have ever seen.

Here's a blog I wrote about DS that you may find helpful.
http://magoosh.com/gmat/2012/introduction-to-gmat-data-sufficiency/

I'll also recommend Magoosh test prep: we have over 200 video explaining all the content & strategy you will need for the GMAT. We have, for example, a whole series on mastering the DS questions. You seem to have a strong background in math, and there's no reason that you can't learn to be successful on GMAT math, but that will take expert training, and Magoosh can really help in this respect.

Here's a sample lesson on Critical Reasoning:
http://gmat.magoosh.com/lessons/579-dissecting-an-argument

I hope all this is helpful. Let me know if you have any further questions.

Mike

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Magoosh GMAT Instructor
http://gmat.magoosh.com/