A rope, cut off the full length (4/5), exactly 15 meters, how many meters is this rope? Calculation formula: how much.
一根绳子，剪去全长的(4/5)，正好剪去了15米，这根绳子长多少米？算式：多少．
<gadget id="calculator">4 / 5</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">15 / (4/5)</gadget>
<output>75/4 = around 18.75</output>

<result>75/4 = around 18.75</result>