#include<bits/stdc++.h>
using namespace std;

#define ll long long

double arr[100015][11-2];
int main()
{
    //ios_base::sync_with_stdio(false);cin.tie(NULL);
    /*
    #ifndef ONLINE_JUDGE
    freopen("input.cpp", "r" , stdin);
    freopen("output.cpp" , "w" , stdout);
    #endif // ONLINE_JUDGE
    //*/
    for(int i = 2 ; i <= 10 ; i++){
        arr[100000][i-2] = (i * 1.0 / (i - 1));
        for(int j = (100000-1) ; j > 0 ; j--){
             double sum = 0.0;
             for(int k = 1 ; k < i ; k++){
                sum = sum + arr[j + k][i-2];
             }
             arr[j][i-2] = (i*1.0/(i - 1))*(1 + 1.0 /i * sum );
        }
    }
    int t;cin >> t;
    while(t--){
        int n , k;
        cin >> n >> k;
        printf("%.9lf\n" , arr[100001-n][k-2]);
    }
    return 0;
}