In some of my math classes we could only use a simple calculator. I couldn't ever remember most of the formulas so i would right them all down on small piece of paper and with black electrical tape, tape them to the back of my black calculator. With the tape I would just make a little tab big enough for me to pinch so that when the instructor wasn't looking I could flip the calculator over, pull back that cheat sheet, get my formula and then seal it back up to work the problem. Helped a lot...