#include<iostream>

 #include<stdio.h>

 #include<stdlib.h>

 #include<memory.h>

 #include<string.h>

 #include<algorithm>

 #include<cmath>

 #define clc(a,b) memset(a,b,sizeof(a))

 typedef long double ld;

 typedef long long ll;

 const int N = ;

 const double eps=1e-;

 const int inf=-;

 const int maxn=1e5+;

 const double Pi=acos(-);

 using namespace std;

 double H,h,D;

 double calc(double x)

 {

     return D-x+H-(H-h)*D/x;

 }

 double solve(double l,double r)

 {

     //cout<<"11"<<endl;

     double mid,midmid;

     double d1,d2;

     while(r-l>=eps)

     {

         mid=(l+r)/;

         midmid=(mid+r)/;

         d1=calc(mid);

         d2=calc(midmid);

         if(d1>=d2)

             r=midmid;

         else

             l=mid;

     }

     return d1;

 }

 int main()

 {

     int t;

     scanf("%d",&t);

     while(t--)

     {

         scanf("%lf%lf%lf",&H,&h,&D);

         printf("%.3lf\n",solve((H-h)*D/H,D));

     }

     return ;

 }