#include <iostream>
#include <stdio.h>
using namespace std;
int main() {
// your code goes here
int t;
cin>>t;
while(t--)
{
int u,v;int x;
cin>>u>>v;
cin>>x;
double ans=(1.0000000000*u/x)+(1.0000000000*v/x);
printf("%.10lf\n",1/ans);
}
return 0;
}
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