For a manuscript, it takes 10 hours for A to type alone, and 15 hours for B to type alone. How many hours will it take for two people to type together?
一份稿件，甲单独打完要用10小时，乙单独打完要用15小时，两人合打要多少小时完成？
<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>