Each team works independently on a project, and A takes 15 days to complete, and B takes 10 days to complete. If two teams work together, how many days can it be completed?
一项工程每队单独做，甲要15天完成，乙要10天完成．如果两队合做，多少天可以完成？
<gadget id="calculator">1 / 15</gadget>
<output>1/15 = around 0.066667</output>

<gadget id="calculator">1 / 10</gadget>
<output>1/10 = around 0.1</output>

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

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

<result>6</result>