Post going through all DS questions from
OG, I have noticed that most of the DS questions are like this. Mostly, the tricky ones can be classified in the following buckets: (its not an extensive list)
1) Post deduction and simplification ,both equations are same or one of the equation is an information set that was already present in the question itself
2) Missing out the possibility of 0 as both being positive and negative
3) 4-5 variables being removed by use of two equations only (GMAT gives questions having variables more than the number of equations, but the even those equations are linked in such a manner that even lesser number of equations are sufficient)
4) square root of a number (if given by GMAT) only considers positive solution only