A task can be completed by team A alone in 10 days, and by team B alone in 15 days. How many days will it take for the two teams to work together?
一项工作，甲队单独做需要10天完成，乙队单独做15天完成．两队合做需要多少天完成．
<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>