One piece of work is done individually, Team A will complete it in 10 days, and Team B will complete it in 15 days. Now the two teams cooperate, how many days can it be completed.
一件工作，单独做，甲队10天完成，乙队15天完成．现在两队合作，多少天可以完成．
<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>