The floor of the classroom is rectangular, 18 meters long and half as wide, what is its perimeter in meters?
教室地面是长方形，长18米，宽是长的一半，它的周长是多少米？
<gadget id="calculator">18 / 2</gadget>
<output>9</output>

<gadget id="calculator">9 + 18</gadget>
<output>27</output>

<gadget id="calculator">27 * 2</gadget>
<output>54</output>

<result>54</result>