A project is completed in 40 days by A alone, and 60 days by B alone. Now A and B cooperate to complete the project. A rests for several days in the middle, and finally completes the task after 27 days. How many days did A rest?
一项工程，甲独做40天完成，乙独做60天完成，现由甲乙合作完成，甲中途休息了若干天，结果经过27天完成任务．甲休息了多少天．
<gadget id="calculator">1 / 60</gadget>
<output>1/60 = around 0.016667</output>

<gadget id="calculator">(1/60) * 27</gadget>
<output>9/20 = around 0.45</output>

<gadget id="calculator">1 - (9/20)</gadget>
<output>11/20 = around 0.55</output>

<gadget id="calculator">1 / 40</gadget>
<output>1/40 = around 0.025</output>

<gadget id="calculator">(11/20) / (1/40)</gadget>
<output>22</output>

<gadget id="calculator">27 - 22</gadget>
<output>5</output>

<result>5</result>