1. The problem statement, all variables and given/known data Find the Average Grain Diameter 2. Relevant equations d= C/NLM 3. The attempt at a solution My instructor hasn't defined what C or M are. I could easily solve this equation if I just knew which numbers I am supposed to substitute in for C and M. NL is the average number of intercepted grains determined by a 3, 3.5in line strategy. The number I have for it is 2.8grains/in. Any clues on to what C and M could stand for?