The first time I took the topscore QR, i scored a 19 and missed 3 questions because I ran out of time. The second practice test, I placed a random answer on questions that I know would take some time to compute and marked it for later. I then returned after I had completed the exam, hence i got a 21 on QR with no questions missed. Plus work on doing random calculations, because it helped me a lot. I actually managed to score a 24 on the 3rd QR on topscore because my speed in calculations increased significantly. Basically faster you learn how to computer = more time to check over your work. Plus put stuff in fractions. Instead of using .125, use 1/8 because stuff cancel out.
Hope this helps,
Richard Wong