#include<stdio.h>

 #include<string.h>

 #include<math.h>

 #define N 1010

 #define max(a,b) ((a)>(b)?(a):(b))

 #define INF 999999999

 double  map[N][N],lowcost[N],cost[N][N];

 int vis[N];/*-1表示该点已经加入，非0表示i和vis[i]的值表示的点构成一条短边*/

 int n;

 typedef struct

 {

     double x,y,w;

 } Point;

 Point point[N];

 double dis(Point a,Point b)

 {

     return sqrt((a.x-b.x)*(a.x-b.x)+(a.y-b.y)*(a.y-b.y));

 }

 void input(void)

 {

     int i,j;

     scanf("%d",&n);

     for(i=; i<n; i++)

         scanf("%lf%lf%lf",&point[i].x,&point[i].y,&point[i].w);

     for(i=; i<n-; i++)

         for(j=i+; j<n; j++)

             map[i][j]=map[j][i]=dis(point[i],point[j]);

 }

 double prim(void)

 {

     memset(cost,,sizeof(cost));

     memset(vis,,sizeof(vis));

     double ans=;

     int e=,i,j;/*e=0表示首先将点0加入集合U*/

     vis[]=-;/*e用来记录新加入的顶点*/

     for(i=; i<n; i++)

         lowcost[i]=1.0*INF;

     for(i=; i<n-; i++)

     {

         double micost=1.0*INF;

         int miedge=-;

         for(j=; j<n; j++)

             if(vis[j]!=-)

             {

                 double temp=map[e][j];

                 if(temp<lowcost[j])

                 {

                     lowcost[j]=temp;

                     vis[j]=e;

                 }

                 if(lowcost[j]<micost)

                     micost=lowcost[miedge=j];

             }

         ans+=micost;

         cost[miedge][vis[miedge]]=cost[vis[miedge]][miedge]=map[vis[miedge]][miedge];

         for(j=; j<n; j++)

             if(vis[j]==-)

                 cost[j][miedge]=cost[miedge][j]=max(cost[miedge][vis[miedge]],cost[j][vis[miedge]]);

                 vis[e=miedge]=-;

     }

     return ans;

 }

 void solve(void)

 {

     int i,j;

     double mst=prim();

    /* printf("%f\n",mst);*/

     double ans=-;

     for(i=; i<n-; i++)

         for(j=i+; j<n; j++)

         {

             double t=(point[i].w+point[j].w)/(mst-cost[i][j]);

             ans=max(ans,t);

         }

     printf("%.2f\n",ans);

 }

 int main(void)

 {

     int t;

     scanf("%d",&t);

     while(t--)

     {

         input();

         solve();

     }

     return ;

 }