I just divide it into quarters. For example, Physical sciences is 70 minutes long, so 17.5, ie 18 minutes per quarter. 52 questions/4= 13 questions per quarter...so after apprxomimately first 20 minutes...i should be done with 13 questions...and by 35 minutes...i should be hopefully more than halfway through...and i know if i slow down a little during one quarter...i have to pick it up and work faster in the next...idk for some reason i can just work fast though...i end up finishing PS with about 25 minutes to spare...