A project can be completed by team A alone in 10 days, and by team B in 15 days. How many days will it take for the two teams to work together to complete the project?
一项工程，甲队单独施工需10天完成，乙队单独施工15天完成，两队合做多少天完成这项工程的？
<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>