DAT Destroyer is meant to teach, not to evaluate. There's a disclaimer on the back of the front cover that acknowledges the difficulty of the problems, and that one should not time him or herself while doing the problems. The Destroyer does not accurately reflect actual DAT problems, but is an excellent tool for picking your weaknesses out. As some have said, however, some problems on the real DAT seemed to have come straight out of the destroyer, so the problem types are still somewhat reflective of the real DAT. Use BC for extra practice and time management. Both are excellent tools that I have used. 🙂