Problem Solving

Although I am OK in Q (Thats what I think since my Q~48-49), the mistakes I make were mostly in "Properties of number" problems (Number series, prime numbers, prime factors, largest prime factor...etc).

I have been constantly monitoring my incorrect area and I found:
Overall 40% of my incorrect problems belong to this type only.

I quickly understand it when I read the answer explanation, problem lies mostly in "How to approach"

Is there a quick guide or some stuff that I can read to improve? I can surely improve my score by 1-2 points if I can work on this area.

Get yourself the Number properties guide by Manhattan GMAT. Hopefully that'll do the trick

I have the same problem, does anyone know if they only sell them at the Mgmat site or also at bookstores?

I'm pretty certain the latest edition is only available on the MGMAT site. The number properties book is good. I was in a similar position. 3 chapters in it helped me out a lot.

I ordered the mgmat series yesterday. I will let you guys know how it is