A project, A and B can complete the project (1/10) in 4 days through cooperation, how many days will it take to complete the whole project?
一项工程，甲乙两组合作4天可完成这项工程的(1/10)，那么完成全工程要多少天．
<gadget id="calculator">1 / 10</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">(1/10) / 4</gadget>
<output>1/40 = around 0.025</output>

<gadget id="calculator">1 / (1/40)</gadget>
<output>40</output>

<result>40</result>