A project alone takes 12 days to complete, B alone takes 15 days to complete, and C alone takes 20 days to complete. How many days will it take for teams A, B, and C to cooperate?
一项工程，甲单独完成需要12天完成，乙单独完成需要15天完成，丙单独完成需要20天完成．如果由甲、乙、丙三队合作需要几天完成？
<gadget id="calculator">1 / 12</gadget>
<output>1/12 = around 0.083333</output>

<gadget id="calculator">1 / 15</gadget>
<output>1/15 = around 0.066667</output>

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

<gadget id="calculator">(1/12) + (1/15) + (1/20)</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 / (1/5)</gadget>
<output>5</output>

<result>5</result>