A project can be completed by A alone in 40 days and B alone in 60 days. Now the two are working together, A in the middle has rested for several days due to illness, so it took 27 days to complete. Ask how many days A has rested.
一项工程，甲单独做40天完成，乙单独做60天完成．现在两人合作，中间甲因病休息了若干天，所以经过了27天才完成．问甲休息了多少天．
<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>