#include <bits/stdc++.h>
using namespace std;
//#define int long long
#define si signed
#define sc(x) scanf("%d",&(x));
#define fi first
#define se second
#define pb push_back
#define P pair<int,int>
#define endl '\n'
#define eps 1e-7
si main()
{
    int t;
    sc(t)
    int n;
    double b;
    int x;
    while(t--){
        sc(n)
        int ma = 0,mb = 2;
        for(int i=0;i<n;i++){
            sc(x)scanf("%lf",&b);

            int d = 100 - (int)(b*100+eps);
            int c = d+x*100;
            if(d*mb>ma*c){
                ma = d;
                mb = c;
            }}
        //cout<<ma<<' '<<mb<<endl;
            printf("%.5f\n",ma*1./mb);


    }
}