I am following up on Stacey's suggestion to ask in the forums about frequency of our question type weaknesses:
http://www.manhattangmat.com/blog/index ... to-review/
How often have the following question types appeared on recent GMAT exams?
Math
FDPs (Ratios, Fractions, and Percents)
Overlapping Sets
Linear Equations
Exponents and Roots
SC
Modifier
Idiom
CR
Explain Discrepancy