#include <bits/stdc++.h>
using namespace std;
const int N = 1e5 + 7;
int n, m, sz[N], dep[N], jp[20][N];
long long sum[N], nsum[N];
int head[N], edge_id;
struct node {
  int to, next;
} e[N << 1];
void add_edge(int u, int v) {
  ++edge_id, e[edge_id].next = head[u], e[edge_id].to = v, head[u] = edge_id;
}
void dfs(int x, int fa) {
  sz[x] = 1, dep[x] = dep[fa] + 1, jp[0][x] = fa;
  for (int i = head[x]; i; i = e[i].next) {
    int v = e[i].to;
    if (v == fa) continue;
    dfs(v, x);
    sz[x] += sz[v], sum[x] += sum[v] + sz[v];
  }
}
void DFS(int x, int fa) {
  long long gg = 0;
  for (int i = head[x]; i; i = e[i].next) {
    int v = e[i].to;
    if (v == fa) continue;
    nsum[v] = nsum[x] + (sum[x] - sum[v] - sz[v]) + (n - sz[v]);
    DFS(v, x);
  }
}
void work(int x, int y) {
  if (dep[x] < dep[y]) swap(x, y);
  int dx = x, dy = y, len = 0;
  for (int i = (18), iE = (0); i >= iE; i--)
    if (dep[dx] - dep[dy] > (1 << i)) dx = jp[i][dx], len += (1 << i);
  if (jp[0][dx] == dy)
    printf("%.10lf\n",
           1.0 * sum[x] / sz[x] +
               1.0 * (sum[y] - sz[dx] - sum[dx] + nsum[y]) / (n - sz[dx]) +
               len + 2);
  else {
    if (dep[dx] != dep[dy]) dx = jp[0][dx], len++;
    for (int i = (18), iE = (0); i >= iE; i--)
      if (jp[i][dx] != jp[i][dy])
        dx = jp[i][dx], dy = jp[i][dy], len += (2 << i);
    dx = jp[0][dx], dy = jp[0][dy], len += 2;
    printf("%.10lf\n", 1.0 * sum[x] / sz[x] + 1.0 * sum[y] / sz[y] + len + 1);
  }
}
int main() {
  scanf("%d%d", &n, &m);
  int u, v;
  for (int i = (1), iE = (n - 1); i <= iE; i++)
    scanf("%d%d", &u, &v), add_edge(u, v), add_edge(v, u);
  dfs(1, 0), DFS(1, 0);
  for (int i = (1), iE = (18); i <= iE; i++)
    for (int j = (1), jE = (n); j <= jE; j++)
      jp[i][j] = jp[i - 1][jp[i - 1][j]];
  while (m--) scanf("%d%d", &u, &v), work(u, v);
  return 0;
}
