ZOJ 3203

#include <iostream>
#include <cstdio>
#include <cstring>
#include <cmath>
using namespace std;

double H,h,D;

double cal(double x){
	return x+(h-x/D*H)*D/(D-x);
}

int main(){
	double ans; int T;
	scanf("%d",&T);
	while(T--){
		scanf("%lf%lf%lf",&H,&h,&D);
		ans=h/H*D;
		double l=0,r=ans;
		double m,mm;
		while(l+(1e-8)<r){
			m=l+(r-l)/3;
			mm=r-(r-l)/3;
			if(cal(m)>cal(mm))
			r=mm;
			else l=m;
		}
		ans=max(ans,cal(l));
		printf("%.3lf\n",ans);
	}
	return 0;
}