#include <bits/stdc++.h>
#include <atcoder/all>
using namespace atcoder;
using namespace std;
using ll=long long;
using ld=long double;
ld pie=3.141592653589793;
ll mod=1000000007;
ll inf=10090000000000000;
int main(){
    ll t;
    cin >> t;
    for (ll o = 0; o < t; o++)
    {
    ld p;
    cin >> p;
    ll k;
    cin >> k;
    vector<ld>x(k+1,0);
    x[1]=p;
    ld now=p;
    for (ll i = 2; i < k; i++)
    {
        x[i]=p*(1.0-now);
        now+=x[i];
    }
    ld ans=0;
    for (ll i = 1; i < k; i++)
    {
        ans+=(ld)i*x[i];
    }
    ans+=k*(1.0-now);
    cout << setprecision(100) << ans << endl;
    }
}