I would not worry too much about the math involved in the General Chemistry section of the DAT. Most question (not all) have the formula as a solution (ex. (298)(67)/(53)) as a solution, not the actual calculated answer. Also, as far as time constraints, the Natural Sciences section is one of the only sections were there is adequate time. The General Chemistry section will definetely take longer than the others, but fortunately Bio and Org Chem sections can be completed quite quickly. Giving you plenty of time to ponder those tough Gen Chem questions.