After building a road for 40 kilometers, there is just 4/5 of the full length left. Find the full length?
修一条路，修了40千米后，刚好还剩下全长的(4/5)，求全长？
<gadget id="calculator">4 / 5</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">1 - (4/5)</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">40 / (1/5)</gadget>
<output>200</output>

<result>200</result>