There is a rope, half of the total length is used for the first time, and the remaining half is more than 0.4 meters for the second time, and 1.8 meters are left in the end. How many meters is this rope?
有一根绳子，第一次用去全长的一半，第二次用去余下的一半多0.4米，最后还剩1.8米．这根绳子长多少米？
<gadget id="calculator">1.8 + 0.4</gadget>
<output>2.2</output>

<gadget id="calculator">2.2 * 2 * 2</gadget>
<output>8.8</output>

<result>8.8</result>