HDU2289——二分——Cup

/*
耐心点推个公式
精度！！！。。。
*/
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <cmath>
using namespace std;

const double esp = 1e-9;
const double pi = acos(-1.0);
int T;
double r, R, H, V;
double check(double x)
{
    double rr = x/H*(R-r) + r;
   // printf("%f\n",rr);
    double V1 = pi/3*x*(rr*rr + r*r + rr*r);
    return V1;
}

int main()
{
    scanf("%d", &T);
    while(T--){
        scanf("%lf%lf%lf%lf", &r, &R, &H, &V);
      //  if(r == R) {
      //     printf("%.6f\n", V/(pi*r*r));
      //     continue;
      //
        double ll = 0, rr = 100, mid;
        while(rr - ll  > esp){
         mid = (ll + rr) / 2;
        double VV = check(mid);
        if(fabs(VV - V) <= esp)
            break;
        else if(VV > V)
            rr = mid - esp;
        else ll = mid + esp;
        }
     printf("%.6f\n", mid);
    }
    return 0;
}