#include <cstdio>#include <cstring>#include <algorithm>#include <queue>#include <stack>#include <map>#include <set>#include <climits>#include <iostream>#include <string>using namespace std; #define MP make_pair#define PB push_backtypedef long long LL;typedef unsigned long long ULL;typedef vector<int> VI;typedef pair<int, int> PII;typedef pair<double, double> PDD;const int INF = INT_MAX / 3;const double eps = 1e-8;const LL LINF = 1e17;const double DINF = 1e60;const int maxn = 60;double f[maxn][maxn][maxn * maxn];bool vis[maxn][maxn][maxn * maxn];int n, m;double dfs(int i, int j, int k) {    int pi = n - i, pj = m - j;    if(i < 0 || j < 0 || k > pi * pj) return 0;    if(i == 0 && j == 0) return k;    if(i == n && j == m) return dfs(i - 1, j - 1, k + 1);    if(vis[i][j][k]) return f[i][j][k];    double rest = n * m - k;    double ret = dfs(i - 1, j - 1, k + 1) * i * j / rest        + dfs(i, j, k + 1) * (pi * pj - k) / rest        + dfs(i - 1, j, k + 1) * pj * i / rest        + dfs(i, j - 1, k + 1) * pi * j / rest;    vis[i][j][k] = true;    return f[i][j][k] = ret;}int main() {    int T; scanf("%d", &T);    while(T--) {        scanf("%d%d", &n, &m);        memset(vis, 0, sizeof(vis));        printf("%.13f\n", dfs(n, m, 0));    }    return 0;}