#include<bits/stdc++.h>
#define MAXN 100000
using namespace std;
int n;
double H,h,D;
double ask(double x) {//返回大的那种情况 
    if(x<=h*D/H) return x+(H-(H-h)*D/(D-x));
    else return x-D+((D-x)*H/(H-h));
}
void three_cut() {//三分，具体原理不懂可以去看模板题题解 
	double l=0,r=MAXN;
	while(r-l>=0.0000001) {
		double lmid=l+(r-l)/3;
		double rmid=r-(r-l)/3;
		if(ask(lmid)>ask(rmid)) r=rmid;
		else l=lmid;
	}
	printf("%.3lf\n",ask(l));
}

int main(void) {
	scanf("%d",&n);
	for(int i=0;i<n;i++) {
		scanf("%lf%lf%lf",&H,&h,&D);
		three_cut();
	}
	return 0; 
}