A batch of 480 tons of goods is transported separately. It takes 20 hours for team A and 30 hours for team B to complete the shipment. Now how many hours will it take for the two teams to complete the joint shipment?
一批货物480吨，单独运，甲队要20小时，乙队要30小时完成，现在两队合运要要多少小时完成？
<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>