Tricks are an attraction of the GMAT. Without tricks and traps, this would have been like the other testing exams. That being said, the tricks don't make this exam any difficult. They make you use your common sense to crack the questions. Brian Galvin, Veritas Prep's Director of Academic Programs, explains a trick to solve feared weighted average GMAT questions.
Source: GMAT Prep
Visit http://www.veritasprep.com/gmat-mba-resources/ for free GMAT resources.