A project can be completed in 20 days alone, and B can be completed in 30 days alone. Now, after a few days of joint training between A and B, there is still one-fifth left?
一项工程甲单独做20天完成，乙单独做30天．现在甲乙两队合修几天后还剩五分之一？
<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 - (1/5)</gadget>
<output>4/5 = around 0.8</output>

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

<gadget id="calculator">1 / 30</gadget>
<output>1/30 = around 0.033333</output>

<gadget id="calculator">(1/20) + (1/30)</gadget>
<output>1/12 = around 0.083333</output>

<gadget id="calculator">(4/5) / (1/12)</gadget>
<output>48/5 = around 9.6</output>

<result>48/5 = around 9.6</result>