20% of a rope is used up, and there are 16 meters left. How long is the rope originally?
一根绳子用去它的20%，还剩16米，这根绳子原来长多少米．
<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">16 / (4/5)</gadget>
<output>20</output>

<result>20</result>