package main

import (
	"bufio"
	"fmt"
	"os"
)

func main() {
	in := bufio.NewReaderSize(os.Stdin, 1<<20)
	out := bufio.NewWriterSize(os.Stdout, 1<<20)
	defer out.Flush()

	var t int
	fmt.Fscan(in, &t)
	for i := 0; i < t; i++ {
		var R, r, k int64
		fmt.Fscan(in, &R, &r, &k)
		num := float64(R * r * (R - r))
		den := float64(R*r + (R-r)*(R-r)*k*k)
		fmt.Fprintf(out, "%.10f\n", num/den)
	}
}