The alcohol solution in the large bottle is twice that of the alcohol solution in the small bottle. The concentration of the alcohol solution in the large bottle is 20%, and the concentration of the alcohol solution in the small bottle is 35%. After mixing the two bottles of alcohol solution, what is the concentration of the alcohol solution?
大瓶酒精溶液是小瓶酒精溶液的2倍，大瓶酒精溶液的浓度是20%，小瓶酒精溶液的浓度是35%，将两瓶酒精溶液混合后，酒精溶液的浓度是多少？
<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">(1/5) * 2</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">35 / 100</gadget>
<output>7/20 = around 0.35</output>

<gadget id="calculator">(7/20) * 1</gadget>
<output>7/20 = around 0.35</output>

<gadget id="calculator">(2/5) + (7/20)</gadget>
<output>3/4 = around 0.75</output>

<gadget id="calculator">2 + 1</gadget>
<output>3</output>

<gadget id="calculator">(3/4) / 3</gadget>
<output>1/4 = around 0.25</output>

<result>1/4 = around 0.25</result>