For a manuscript, it takes 20 minutes for A to type alone, 15 minutes for B to type alone, and how many minutes does it take for two people to type together?
一份稿件，甲单独打要20分钟，乙单独打要15分钟，两人合打要几分钟完成？
<gadget id="calculator">9 / 60</gadget>
<output>3/20 = around 0.15</output>

<gadget id="calculator">1 / (3/20)</gadget>
<output>20/3 = around 6.666667</output>

<result>20/3 = around 6.666667</result>