I assume that most people here have spent many long nights struggling to solve difficult math and science homework problems. What was one of the worst or most memorable problems, and why? The one that stands out the most for me was really not too difficult, but for the longest time I just couldn't see the answer. No matter what I did the answer kept coming out the same - a complex number. Now I knew that the answer had to be real since the value related to a physical quantity, but how to get there from here??? After stewing on this problem for many hours over a period of several nights, it finally hit me. The key was to recognize that I could ignore the imaginary part and use only the real part as the solution. From there the rest was easy. Having solved the problem on the first pass and then spending hours and hours staring and recalculating, I will NEVER make that mistake again.