Try some of the SAT math books. The DAT math questions are often a little trickier, but the good SAT math books will tell you how to go about solving many of the standard math format question types - i.e. train leaving late and catching up, two hoses filling a swimming pool, how many yards of carpeting do you need, etc.
An SAT math question may ask something like John can paint a house in 6 hours and Bob can paint it in 5 hours. How long does it take them working together?
The DAT version might be something like John can paint a house in 6 hours and Bob can paint it in 5 hours. If they get into an argument, and Bob quits half way through, how long does it take to paint the house.
Even though its harder, you can adapt what you learn from the more basic question styles.