A container has a capacity of 20 gallons and is full of spi

First of all I think it should be 20 gallons instead of 200 in order the answer to be B.

Note that 4 gallons is 20% of a capacity. Now, when we remove 20% of spirit for the first time 80% of spirit is left --> when we remove 4 gallons of the mixture for the second time, or again 20% of the capacity, we still remove 20% of the remaining spirit with it (this 4 gallons of the mixture, which is 20% of the capacity, contains 20% of the remaining spirit), so again 80% of the spirit is left... So every time we remove 4 gallons, we re move 20% of the remaining spirit and 80% is left. So after 5 removals there will be 20*0.8^5 gallons of spirit left: \(20*(\frac{4}{5})^5=\frac{4^6}{5^4}= 6\frac{346}{625}\).

Answer: B.

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