If 20% of an iron wire is cut off, there is still 4 meters left. How many meters is this iron wire originally?
一根铁丝截去它的20%后还剩4米，这根铁丝原来长多少米？
<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 - (1/5)</gadget>
<output>4/5 = around 0.8</output>

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

<result>5</result>