#include<bits/stdc++.h>
using namespace std;
float w=0;
double ans(float n,float m)
{
    if(m>=2)
    {
        return n/(n+m)+(m/(n+m))*(m-1/(n+m-1))*ans(n,m-2);
    }
    else
    {
        return n/(n+m);
    }
}
int main()
{
    int t;
    cin>>t;
    while(t>0)
    {
     int n,m;
     cin>>n>>m;
     float a,b;
     a=n;
     b=m;
     float k;
    // float k=a/(a+b);
     /*int e=k;
     if(e==1)
     k=1.000000;
     */
     if(n==0||m==0)
     k=1.0;
     else
     k= ans(a,b);
      cout<<fixed<<setprecision(6)<<k<<endl;
 
 
 
        t--;
    }
}

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10
1 0
0 0
0 1
1000 0
0 1000
999 999
882 456
345 234
12 45
345 56