A project, team A completes the entire project (1/10) every day alone, and team B completes the entire project (1/15) every day alone, how many days can the two teams cooperate to complete the entire project?
一项工程，甲队单独做每天完成全工程的(1/10)，乙队单独做每天完成全工程的(1/15)，两队合作多少天可以完成全部工程？
<gadget id="calculator">1 / 10</gadget>
<output>1/10 = around 0.1</output>

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

<gadget id="calculator">(1/10) + (1/15)</gadget>
<output>1/6 = around 0.166667</output>

<gadget id="calculator">1 / (1/6)</gadget>
<output>6</output>

<result>6</result>