To build a road, the full length (1/5) was built in the first 4 days. According to this calculation, how many days will it take to finish the road.
修一条公路，前4天修了全长的(1/5)，照这样计算，修完这条路还要多少天．
<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">4 / (1/5)</gadget>
<output>20</output>

<gadget id="calculator">20 - 4</gadget>
<output>16</output>

<result>16</result>