10491

很简单的一道题目，概率分析之后列出最终的公式计算即可，具体实现见如下代码：

#include<iostream>#include<vector>#include<string>#include<set>#include<stack>#include<queue>#include<map>#include<algorithm>#include<cmath>#include<iomanip>#include<cstring>#include<sstream>#include<cstdio>#include<deque>#include<functional>using namespace std;int main(){double a, b, c;while (cin >> a >> b >> c){double up = a*b + b*(b - 1);double down = (a + b)*(a + b - c - 1);printf("%.5lf\n",up/down);}return 0;}