import java.util.*;

public class Main{
    public static void main(String[] args){
        Scanner in = new Scanner(System.in);
        int T = in.nextInt();
        for(int cas = 0; cas < T; cas++){
            int n = in.nextInt();
            int[] b = new int[n];
            int[] p = new int[n];
            for(int i = 0; i < n; i++){
                b[i] = in.nextInt();
                String s = in.next();
                p[i] = getInt(s);
            }
            System.out.println(String.format("%.5f",  solve(b,p)));
        }
    }
    
    static double solve(int[] b, int[] p){
        double res = 0;
        for(int i = 0; i < b.length; i++){
            p[i] = (100 - p[i]);
            res = Math.max(res, p[i] * 1.0 / (b[i]*100 + p[i]));
        }                    //System.out.println(res);
        return res;
    }
    
    static int getInt(String s){
        if(s.charAt(0) == '1')
            return 100;
        int pos = s.indexOf('.');
        if(pos < 0)
            return  0;
        int number = 0,  k = 10;
        for(int i = pos+1; i < s.length(); i++){
            number += k * (s.charAt(i)-'0');
            k = 1;
        }
        return number;
    }
            
            
}