The only formal math that you need for the DAT is pre-calculas, either college pre-calc or AP pre-calc from high school.
The key to doing well on the QR section is learning a ton of "tricks" that quickly nails problems without a calculator, and a ton of practice problems. The QR section moves so fast that you really don't have time to figure out how to do problems, you already need to know how solve a ton of different types of problems.
I just kept doing Kaplan and Barrons QR practice problems over and over again until it became second nature how to solve about 40 different types of problems.