There is alcohol in a certain container, the teacher asked Xiaohong to pour 800 grams of alcohol with a concentration of 5% to make alcohol with a concentration of 20%, but Xiaohong poured 800 grams of water by mistake, the teacher said after finding out , it doesn’t matter, if you pour 400 grams of the third alcohol, you can get alcohol with a concentration of 20%, so what is the concentration of the third alcohol?
某容器中装有酒精，老师让小红再倒入浓度为5%的酒精800克，以配成浓度为20%的酒精，但小红却错误地倒入了800克水，老师发现后说，不要紧，你再倒人第三种酒精400克，就可得到浓度为20%的酒精了，那么这第三种酒精的浓度是多少？
<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">400 * (1/5)</gadget>
<output>80</output>

<gadget id="calculator">5 / 100</gadget>
<output>1/20 = around 0.05</output>

<gadget id="calculator">800 * (1/20)</gadget>
<output>40</output>

<gadget id="calculator">80 + 40</gadget>
<output>120</output>

<gadget id="calculator">120 / 400</gadget>
<output>3/10 = around 0.3</output>

<result>3/10 = around 0.3</result>