How do you approach a question that you have no idea what they are asking. Also, let's say that you are running out of time and have a few difficult questions left...when should we start guessing? 5 min left/10 min/?
You should AT LEAST be able to knock out one of the answers because its is an outlier, wrong units, terrible wording. But something should stand out on one of the answer if not two. If you honestly have no clue after that then your down to 1/2 or 1/3 of a chance. If you have more time try and reason your way through it if you can look at the passage. I would say if you only have 5 minutes left for a whole passage. Then just mark all of them so you can get points if you have a brain lapse and run out of time. Then either find some of the questions that you can reason through and do that or skim the passage. Get a general idea and start to attack the problems.
Take up to as much time as you think it will take you to randomly guess on those problems which you have not answered. I'd think it would not take more than 5 minutes max to scroll through and randomly make selections. You don't get penalized for a false answer, so might as well take a shot at it.
I was reading somewhere that a random guess might actually be better than sitting and trying to figure out the problem, because you try to reason through the problem and by doing so eliminate viable answers. I'm not saying do this for all of them, but if you absolutely don't know the answer it's best just to guess.