section of the road is 30 kilometers long. Team A can complete it in 10 days alone, and team B can complete it in 15 days. How many days can the two teams complete together?
一段路长30千米，甲队单独修10天完成，乙队单独修15天完成，两队合修几天可以完成？
<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>