There is a math section in the standard DAT Destroyer book. I did those and wanted more and got the Math Destroyer. The problems in there are more difficult than the ones in the DAT Destroyer, but I think it's good practice so far (I kind of like doing them actually). I have been doing them without timing myself because a lot of the concepts, although they are 'simple' to some, are fuzzy in my memory. Also, some of them can be involved and I think that once I am comfortable with them, the real thing should be similar if not easier (well, hopefully anyways).