A container is exactly filled with 10 liters of pure alcohol. After pouring out 4 liters, it is filled with water and stirred evenly. After pouring out 3 liters, it is then filled with water. What is the concentration of the solution in the container at this time?
一个容器正好装满10升纯酒精，倒出4升后用水加满并搅拌均匀，再倒出3升后，再用水加满，这时容器中溶液的浓度是多少？
<gadget id="calculator">10 - 3</gadget>
<output>7</output>

<gadget id="calculator">10 - 4</gadget>
<output>6</output>

<gadget id="calculator">6 / 10</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">(3/5) / 10</gadget>
<output>3/50 = around 0.06</output>

<gadget id="calculator">7 * (3/50)</gadget>
<output>21/50 = around 0.42</output>

<result>21/50 = around 0.42</result>