1.8 meters of a rope are used up, and the rest is 0.5 meters more than what was used. What is the original length of the rope?
一根绳用去1.8米，剩下的比用去的多0.5米，这根绳原来长多少米．
<gadget id="calculator">1.8 + 0.5 + 1.8</gadget>
<output>4.1</output>

<result>4.1</result>