These questions are easy and quick solves if you know how to approach them. The problem is that learning different approaches to this topic requires a lot of practice. Make sure to solve around 300 questions of Number Series on different patterns. Once you gain some familiarity with all types of questions in this, you will start seeing the patterns with greater confidence. In exam if you don't get the pattern in 30 sec then don't waste time on it, just move on.