import heapq
from itertools import product
from itertools import permutations
import random
import math
import bisect
import sys
from collections import defaultdict
from itertools import combinations


inf = 1 << 60


def exit():
    sys.exit()


def LI():
    return list(map(int, input().split()))


def II():
    return int(input())


def SI():
    return input()


t = II()
for _ in range(t):
    n, m, k = LI()
    if n*m//2 >= k:
        print((n*m-1)/(n*m))
    else:
        print((n*m-1)/(n*m)/2)