A project can be completed by A alone in 10 days, and B alone can only complete (2/3) of the project in 10 days. If A and B cooperate, how many days can it be completed?
一件工程，由甲单独做10天完成，乙独做10天只能完成这项工程的(2/3)，如果甲乙合作，多少天可以完成．
<gadget id="calculator">1 / 10</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">2 / 3</gadget>
<output>2/3 = around 0.666667</output>

<gadget id="calculator">(2/3) / 10</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>