Dig a 3 km long canal, digging (1/4) of it every day, how many days can be completed.
挖一条3千米长的水渠，每天挖它的(1/4)，多少天可以挖完．
<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

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

<result>4</result>