We can begin by using the inverse variation formula, which states that:
t = k/G
where t is the time it takes to put out the fire, G is the volume of water used, and k is a constant of variation.
We can find the value of k by using the given information that when G is 8, t is 12:
12 = k/8
Multiplying both sides by 8, we get:
k = 96
Now that we know the value of k, we can use it to find how long it takes to put out a fire when 200 gallons of water are used (G = 2):
t = 96/G
t = 96/2
t = 48
Therefore, it would take 48 minutes to put out the fire using 200 gallons of water.