I don't have this particular problem, but you should use all of the information provided to you. I took AAMC 4 tonight and got a 39 w/ a 14 on the PS. There was one section based on a % solution by wt/wt. I had NO idea what this was (well I had an ok idea, % wt solute/wt solution, but I didn't want to go through the calculations) and I was kind of jammed for a second but I came to realize there was a chart with all of the info I needed. I didn't miss a single question on that passage. Bottom line is you can never have too much info when tackling these problems, so you might as well make the best of what you've got.