When my kids were younger, we did a lot of math games to help learn and understand the concepts. But when they got to the point where they had to do timed math tests (i.e 30 or 40 problems in a minute), we had to break out the flash cards. That was the only way they were able to memorize them and answer quickly. We started with the 0's, 1's & 2's. Then added the 3's into the mix. Once those were quick, we added the 4's. And so on. If there were any problems that they had trouble with, we pulled those cards out and went over them at the end. We spent 5 to 10 minutes each night going through the cards and they eventually got them.