I was doing my algebra homework once, and I couldn't remember the equation that I needed. However, I was able to recognize that it was really just a somewhat complex conversion problem. So, I used the conversion "equations" from chemistry (grams-moles, etc), and solved the problem.
A couple of days later, he called for me after class. He was holding my homework in his hand, red-faced, shaking, trying to point at my homework while crumpling it at the same time, and said "DON'T YOU EVER DO A MATH PROBLEM LIKE THIS IN MY CLASS AGAIN!" I thought he was going to have a coronary. LOL.
LOL! That is a great story! *sigh* College days -- the best days of our lives.