Hi ecobiz.
GMAT quant questions are designed to be answered in various ways, from using formal algebra to picking numbers or testing the answer choices. Overall, what these questions are designed to test, in addition to a test-taker's facility with math, are vision, execution skills, and skill in using resources to arrive at solutions.
Accordingly, different test-takers with different styles will arrive at the answers to quant questions in different ways. Some test-takers, such as people who have been focused on developing their math skills for much of their lives, prefer to use algebra, formulas, or other relatively math heavy approaches in answering the questions. Others prefer to use simple hacks that get them to the answers without much math.
Some GMAT preparation materials focus on the former type of approach. Others focus on the latter. While, clearly, you could learn to use any type of approach, your quickest path to attaining your GMAT score goal is to use the type of approach that is most comfortable for you, as long as that approach is consistently effective.
That said, it could be that the materials you have been using do not explain the approaches in a way that makes them clear for someone who does not already have a certain level of understanding of the concepts. So, you might be better off using different materials.
In any case, preparing for the GMAT is usually a fairly significant endeavor, and what you are experiencing is just another part of the process of finding your way to GMAT success. So, my suggestion is that you assume that you can hit your score goal and continue to look for approaches to doing so that work for you.
For some ideas on how to increase your GMAT quant score, you could read the following post.
How To Increase Your GMAT Quant Score _________________
Marty Murray | Chief Curriculum and Content Architect
See why Target Test Prep is the top rated GMAT course on GMAT Club.
Read Our Reviews