A project alone takes 10 hours to complete, and B alone takes 15 hours to complete. Two people working together, how many hours to complete half of the project?
一项工程，甲独做要10小时完成，乙独做要15小时完成．两人合做，几小时完成这项工程的一半？
<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</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">(1/2) / (1/6)</gadget>
<output>3</output>

<result>3</result>