I preview the 11 science passages, and answer the 15 free responses first. That way, the last 5 questions(i.e 73-77) of the exam will be answered.
As for the rest of the passage, if you have to pick your battles, leave calculation questions to the end. Come back to them. Just put a HUGE circle around the problem for easy identification later.
You don't want to lose time and jeopardize missing an easy question like which of the following has the highest electronegativity by trying to dig up equations for a block on an incline plane(i.e is that cos or sin of G for Normal force). Not that it matters, NF=G cos theta.