Two engineering teams, A and B, repair the same road. Team A alone will take 20 days to repair it, and Team B will take 30 days to repair it alone. If the two teams work together how many days to complete.
甲、乙两个工程队修同一条公路，甲队单独修要20天，乙队单独修要30天．如果两队合修多少天完成．
<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>