for _ in range(int(input())):
    t, m, l = map(float, input().split())
    # vt+v^2/20m=l
    # v^2 +20mt v -20ml=0
    # v=-10mt + sqrt((10mt)^2+20ml) = 20ml / (10mt + sqrt((10mt)^2+20ml))
    ans = 20 * m * l / (10 * m * t + ((10 * m * t) ** 2 + 20 * m * l) ** 0.5)
    ans = ans * 60 * 60 / 1000
    print(f'{ans:.2f}')