GMAT Math

I'm very restricted in time. My quant scores with no study in the gmet prep and manhattan were between 36-44. I want to pump this score up as much as possible. I'm weaker in DS than PS, 2/3 of my wrong answers were DS.
I plan to do most if not all of the OG questions even though if I find the first batch of questions too easy I might skip to harder ones.

I read through the beat the gmat strategy guide. The 790 guy and Ursula blogs made an impression, they complement each other and will be my base as I study 8hrs per day for the next 3 weeks to take my score from 640-680 to 720+. So I want to increase my score in the quant. as quickly as possible as I see most ppl that end up with 700+ are in the high 40s in their quant score. In verbal the only area that I will focus on is SC.

Both of them (Eric & Ursula) used the Kaplan Gmat Math Workbook plus other resources. I wanted to check here first before I go and buy one to see if there is any consensus on the one extra book that is a must for the quant section and will make the biggest difference in the shortest period of time.

Cheers

All of the Manhattan GMAT's strategy guides(5 for math dealing with different topics) are good supplments to the OG.


Regards,
CR