import java.io.*;
import java.util.*;
class CLATTK{
    public static void main(String args[])throws Exception{
        Scanner sc = new Scanner(System.in);
        int T = sc.nextInt();
        while(T-->0){
            int H = sc.nextInt();
            int W = sc.nextInt();
            double out = calculate(H, W);
            System.out.printf("%.7f%n",out);
        }
    }
 
    static double calculate(int H, int W){
        long sum = W*W*(H-1);
        long a = W-1;
        long b = W-(H-1);
        long n = W-H;
        if(n>0)
            sum += 2*(n*a*b + n*(n+1)*(2*n+1)/6 - (a+b)*n*(n+1)/2);
        return (double)sum/(W*W);
    }
}
 

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