// Arup Guha
// 2/23/2016
// Solution to 2016 FHSPS Playoff Problem: Flagpoles

/***
  	The solution to this problem involves setting up two sets of similar triangles.
  	The right triangle with legs a and d is similar to the smaller right triangle
  	with height h and distance x (unknown), while the right triangle with legs
	b and d is similar to the smaller right triangle with height h and distance d-x.
	This creates two ratios:

	h/a = x/d and h/b = (d-x)/d

	Adding these two equations, we get h/a + h/b = x/d + (d-x)/d = (x+d-x)/d = 1.
	Thus, h*(1/a+1/b) = 1. It follows that h = ab/(a+b)
***/

import java.util.*;

public class flagpoles {

	public static void main(String[] args) {

		Scanner stdin = new Scanner(System.in);
		int numCases = stdin.nextInt();

		// Process each case.
		for (int loop=0; loop<numCases; loop++) {

			int a = stdin.nextInt();
			int b = stdin.nextInt();
			int d = stdin.nextInt();

			// Note that changing d doesn't change the answer!!!
			System.out.printf("%.3f\n", (((double)a)*b)/(a+b));
		}
	}
}