A project can be completed by team A alone in 20 days and by team B in 30 days. How many days will it take for teams A and B to complete half of the project?
一项工程，甲队单独做要20天完成，乙队单独做要30天完成．若甲、乙两队完成工程的一半，需要多少天．
<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>