A project can be completed in 10 days by A alone, and 15 days by B alone. If two teams work together, how many days can they complete the project?
一项工程，甲独做10天完成，乙独做15天完成，两队合做，多少天可以完成这项工程．
<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>