I'm happy to help with this.

As a general and very rough rule, the questions toward the ends of sections of the OG tend to be more challenging on average and the questions toward the beginning tend to be more accessible. Having said that, exceptions abound. There is absolutely no guarantee that, problem by problem, each one is incrementally harder than the one before it. It's certainly not that exact or that specific. Furthermore, among us GMAT prep folks, it's almost a joke, for example, that the final DS question in the guide (for at least three editions in a row) has been this silly question involving "Marcia's bucket" --- clearly not the hardest DS in the whole guide, and yet for some indiscernible reason, it's the last in that section of the OG.

I would say --- use the question number as a very rough indication of the level of difficulty --- for example, it's reasonably likely that, say, question #105 of any section will be harder than, say, question #13 of that same section. But don't think that question #57 absolutely must be more difficult than, say, question #51. It's a very approximate trend, not an exact rule by any means, so much so that, for example, there's no reliable way to predict difficulty with any two problems on the same page.

Does all this make sense?

Mike
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Mike McGarry
Magoosh Test Prep