Hi iliavko,
Maybe I can help a little bit since I also had difficulties with maths. And after spending my first two months reviewing my basic maths I only got a Q37. Yet after 6 months of relentless efforts I managed to score a Q48. It is not easy but it can be done.
If you really struggle with Quant on the GMAT and your maths is rusty, the first thing to do before attacking the GMAT is actually to
learn basic maths concepts. To get a 700+ with a decent quant score, you need not only to know by heart your maths formulas and basics but you'll need to know how to apply them to the GMAT.
I'll give you a couple of examples of maths concepts you should understand before even going into GMAT questions:
- can you solve equations with two variables ?
- do you know how to calculate a % change ? (e.g: what's the % change between 67,5 in year 1 and 89 in year 2 ?)
- do you know the formula for calculating the area and perimeter of a circle, a rectangle, a square ?
- do you know the rules relating to exponents and square roots ?
- can you easily and quickly add fractions together ?
- can you easily and quickly calculate simple probabilities question ?
The point I'm trying to make is that, as explained by BB in his Study Plan post, you have to build your foundations first. If the above questions seem hard you first need to spend time on your basic formulas and on practising basic maths skills. Personally I spent 2 months reviewing my basics before actually moving into GMAT questions. Otherwise, solving a GMAT quant question in two minutes will be extremely hard. Also you risk wasting your OG and GMAT Prep questions and tests.
To sum up:- So I would recommend getting a mid-school / high school maths book to get those basics. You can also use GMAT Club Maths Workbook which has all the essential theory but you may need the additional explanations from other books. Use the iphone App Mental Maths if you have an iphone (but I'm sure similar apps exist for other smartphones).
- Then start practising with GMAT problems (start with the easy ones a) and look for Bunuel's explanations, they'll really help.
- If you hit a plateau in terms of score and you have mastered the basic maths I would suggest looking into a tutor for a couple hours, it did the trick for me. But note that it'll be a waste to pay for a GMAT tutor now, a GMAT tutor is only worth it once you've exhausted all possibilities to improve on your own.
For materials :
Magoosh has great videos to teach you maths. And you might want to look into
MGMAT Foundations of Maths book.
Best of luck.