Team A and Team B are building a road. Team A alone will complete the repair in 20 days, and Team B will complete the repair in 30 days. How many days will it take for both teams to build the road at the same time?
甲队和乙队修一条公路，甲队单独修20天完成，乙队单独修30天完成，甲乙两队同时修这条公路多少天能完成？
<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>