A project alone takes 10 days and B takes 15 days to complete. If A and B cooperate for how many days, (2/3) of the whole project can be completed.
一项工程甲独做要用10天，乙要15天才能完成．如果甲乙合作多少天，可以完成全工程的(2/3)．
<gadget id="calculator">2 / 3</gadget>
<output>2/3 = around 0.666667</output>

<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">(2/3) / (1/6)</gadget>
<output>4</output>

<result>4</result>