Zhangcun plans to build a new road. There are two engineering teams, the first team will complete the repair in 20 days alone, and the second team will complete the repair in 30 days alone. If the two teams work together, how many days can it be completed?
张村准备新修一条公路．两个工程队，一队单独修20天完成，二队单独修要30天完成．如果两队合修，多少天能修完？
<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 / (1/12)</gadget>
<output>12</output>

<result>12</result>