4 meters of a rope have been used, and the rest is 20% of the used length. How long is the rope in meters?
一根绳子，用去了4米，余下的是用去的20%，这根绳子长多少米．
<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 + (1/5)</gadget>
<output>6/5 = around 1.2</output>

<gadget id="calculator">4 * (6/5)</gadget>
<output>24/5 = around 4.8</output>

<result>24/5 = around 4.8</result>