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

int main()
{
	int T;
	cin >> T;
	while (T--)
	{
		int n, k;
		cin >> n >> k;
		double maxx = 0.0;
		double cnt = 0.0;
		double qian = 0.0;
		for (int i = 1; i <= n; i++)
		{
			cnt = k + (qian / i);
			qian = cnt;
			if (cnt > maxx)
			{
				maxx = cnt;
			}
		}
		printf("%.1lf\n", maxx);
	}
	return 0;
}