by christiancryan Tue Sep 25, 2007 11:00 am
We can't assign an exact number, of course. To assign problems to the Challenge Sets, there are essentially three principles we used:
1) Do we think it's hard?
2) Does the GMAT think it's hard?
3) Do we have a balance of topics?
The answer to question 1 is subjective, but born of our experience. The answer to question 2 is transparent: the OG books list the problems in order of difficulty -- a characteristic that the GMAT folks measure easily, in their position as test administrators. So, higher number = more difficult from the GMAT's point of view. But they don't say "this is a 670 problem," as you know. Question 3 comes in to ensure that someone doing a Challenge Set gets broad exposure to the topics.
So, where does that leave us? If I had to draw a rough line, I'd put it at 600 and say that the Challenge Problems are mostly at or above that level.
Hope that's helpful!