I am looking on the Jeff Sackmann website and I see the Extreme Challenge, Data Sufficiency Challenge, and Problem Solving Challenge. Is there any overlap in the EC, and the DSC and the PSC? Are all three of these helpful? I have read on here that the EC is very useful, but what about the other ones. I am asking becuase there is a deal for the more you buy, so before doing so, I want to get feedback on the DSC and the PSC first.
I'd go ahead and contact Jeff. He's generally responsive to questions about his products.
I don't think anyone here has purchased the complete set from him.
Here is some general info about Jeff's math products:760-q49-v44-my-gmat-progress-diary-78853.html?view-post=617183#p617183
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