A project can be completed by team A alone in 15 days; team B alone can be completed in 10 days. Two teams cooperate, how many can be completed every day.
一件工程，甲队单独做，15天完成；乙队单独做，10天完成．两队合作，多少天天可以完成．
<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>