To print a manuscript, it takes 40 minutes for Xiao Wang to type alone, and half an hour for Xiao Li to type alone. If two people cooperate to type this manuscript, how long will it take to finish this manuscript?
打印一份稿件，小王单独打需40分钟，小李单独打需半小时．如果两人合作打这份稿件，多长时间可以打完这份稿件？
<gadget id="calculator">1 / 40</gadget>
<output>1/40 = around 0.025</output>

<gadget id="calculator">1 / 30</gadget>
<output>1/30 = around 0.033333</output>

<gadget id="calculator">(1/40) + (1/30)</gadget>
<output>7/120 = around 0.058333</output>

<gadget id="calculator">1 / (7/120)</gadget>
<output>120/7 = around 17.142857</output>

<result>120/7 = around 17.142857</result>