Discipline + Hard Work = Success! 770 (Q50, V46) [updated]

Comb/Prob did give me some issue, but you basically just have to know the classic permutation or combination formula (5 people, 3 spots, arrangement doesn't matter: 5!/(3!*2!); arrangement does matter: 5!/3!), and probability is (# of successful outcomes)/(# of total outcomes) and you should be fine.

I always tried to pace myself to give myself about 3-4 minutes to answer math questions I found more difficult than others (set theory, rates/work, VIC's, coordinate-plane DS questions), so I would be able to test answer choices, double-check my math, etc. Towards the end of my basics-building studies I was honestly getting a bit overwhelmed by all of the math shortcuts and rules—I'd review all 5 MGMAT books, and the more I'd learn on Geometry, the more I'd forget on Number Properties. I tried to rectify this by working on pacing and algebra word translations instead. Even if you forget the shortcuts, you can generally solve a problem in 4-5 minutes. The only problem is making sure that you're only stuck on 2-3 of those problems per exam.

To be honest, I don't recall seeing a comb/prob, but there could very well have been an easy one that I breezed through. If anything all of the ones I came across during my OG and GMATPrep were nowhere near as difficult as any of the MGMAT examples. I think the GMAT tries to leave these questions easy so somebody without any Comb/Prob practice can draw out all of the choices and determine these via longhand.