project is done alone. Team A will complete it in 10 days, and Team B will complete it in 15 days. Now that teams A and B are working together on this project, how many days will it take?
一项工程，单独做，甲队要10天完成，乙队要15天完成，现在甲、乙两队合做这项工程，需要几天？
<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>