### Bookshelf

 Total GMAT Math Jeff's complete Quant guide, on sale now!
 Total GMAT Verbal Everything you need to ace GMAT Verbal!

1,800 Practice Math Questions

GMAT Official Guide, with IR
OG Math | OG Verbal
OG12 & Quant Rev solutions!

GMAT Question of the Day
Beginner's Guide to the GMAT
GMAT Hacks Affiliate Program

## Video: OG Diag Explanation: DS #39

###### August 6, 2010

 You should follow me on Twitter. While you're at it, take a moment to subscribe to GMAT Hacks via RSS or Email.

Today's video covers another Data Sufficiency question from the diagnostic test of the Official Guide.

This one is a tricky coordinate geometry example. It demands an intuitive understanding of slope. Calculating slope is one thing, but handling different slopes and their ramifications is much more demanding.

In the video, I explain how to attack this particular problem, and also talk about some of the key insights the GMAT requires in coordinate geometry.

Remember, I've created (print) explanations to every Quant problem in The Official Guide for GMAT Review and The Official Guide for Quantitative Review. Find out more about those resources here.

About the author: Jeff Sackmann has written many GMAT preparation books, including the popular Total GMAT Math, Total GMAT Verbal, and GMAT 111. He has also created explanations for problems in The Official Guide, as well as 1,800 practice GMAT math questions.

 Total GMAT Math The comprehensive guide to the GMAT Quant section. It's "far and away the best study material available," including over 300 realistic practice questions and more than 500 exercises! Click to read more.