The principles of competition are fairness and reasonableness. However the authorities in charge often set up the total score formulae according to their own experiences and instincts. What is the mathematical meaning of such formulae? Can the total scores reflect the competitors' abilities? How to re-rank the competitors when they have the same total score? A reasonable and simple scoring formula is derived and submitted in this paper. Some typical formulae in current use are also categorized and analyzed. There are only two parameters in the proposed formula, which are q and r respectively. Both the mathematical and the physical meaning of the two parameters are well-defined, so the authorities concerned can refer to establish the competition rules or use them directly with ease.