It takes 20 days for the road construction team to build a road, and it takes 30 days for the second team to complete it alone. If the two teams cooperate. How many days will it take to complete half of the task?
筑路队修一条公路，一队独修需要20天完成，二队独修需要30天完成．如果两队合作．需要多少天才能完成任务的一半？
<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</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">(1/2) / (1/12)</gadget>
<output>6</output>

<result>6</result>