You're kidding, right? I think that some guys waste too much time going to school that would be better spent riding their bicycles. this looks to me like a case where just doing the math is going to give you a wrong answer.

uppose you start at the top of a mile high hill. Coast down the hill, ride around the bottom and climb back up the other side. Since you started and ended in the same place, the percent of grade for the whole ride is zero. The steepness of the last little uphill segment is what is going to determine how hard the ride is.