8.4. Sasha is a coffee lover who drinks coffee at work, so every morning before work, he prepares a thermos of his favorite drink according to a strict ritual. He brews 300 ml of the strongest aromatic coffee in a Turkish coffee pot. Then Sasha repeats the following actions 6 times: he pours 200 ml from the pot into the thermos, and adds 200 ml of water to the pot, and mixes thoroughly. After the 6th time, Sasha pours all 300 ml from the pot into the thermos. What will be the concentration of the original strongest aromatic coffee in the thermos? Initially, the thermos is empty.

The concentration is a number from 0 to 1. Provide the answer as a fraction (common or decimal), not as a percentage.

Answer, option 1. 0.2 .

Answer, option 2. 0.2 .

Answer, option 3.0 .2 .

Answer, option 4. 0.2 .
Solution option 1. Note that by the end of the ritual, there will be 200 ml of coffee and 800 ml of water in the thermos. Therefore, the concentration of coffee is $200 / 1000 = 1 / 5 = 0.2$.

Remark. One could try to solve the problem "step by step": calculate the concentration of coffee in the thermos after the first transfer, after the second, and so on. With such an approach, complex expressions are obtained, and the probability of solving the problem correctly is minimal.