Skim the passage, you should be able to quickly determine if it's a straightforward one on a familiar topic or a curveball on something you've not seen much before (there's usually one or two weird, dense passages per section). If it's a weird one, really read it.
Then do the problems, referring to the passage as needed. Total time per should be about 7 minutes on average (that leaves you a few extra minutes for the tougher passages and double checking the toughest problems). Discretes should be like 30 seconds each.