A project is completed in 6 days by Party A alone, and 4 days by Party B alone. How many days will it take for the two parties to cooperate to complete the project?
一项工程，甲方单独施工6天完成，乙方单独施工4天完成，两方合作多少天完成这项工程．
<gadget id="calculator">1 / 6</gadget>
<output>1/6 = around 0.166667</output>

<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">(1/6) + (1/5)</gadget>
<output>11/30 = around 0.366667</output>

<gadget id="calculator">1 / (11/30)</gadget>
<output>30/11 = around 2.727273</output>

<result>30/11 = around 2.727273</result>