A project can be completed in 10 days by A alone, and 15 days by B alone, how many days will the two work together to complete it?
一件工程，甲独做10天完工，乙独做15天完工，二人合做几天完工？
<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>