The Chibi War was about to start, but the coach Zhou Yu found that there were not enough bows and arrows, and there were still 30,000 bows! So Lu Su and Zhuge Liang were ordered to make it. Lu Su said that the people he led would need 30 days to complete the project; Zhuge Liang said that the people he led would only need 20 days to complete the project. If two teams cooperate, how many days will it take to complete.
赤壁大战一触即发，主帅周瑜却发现弓箭不够，还差整整三万支！于是命令鲁肃、诸葛亮制造，鲁肃说他带领的人需要30天才能完工；诸葛亮说他带领的人仅仅需要20天就能完工了．如果两队人合作，需要多少天能完成．
<gadget id="calculator">1 / 30</gadget>
<output>1/30 = around 0.033333</output>

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

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

<gadget id="calculator">1 / (1/12)</gadget>
<output>12</output>

<result>12</result>