Uncle Wang wants to use a 24-meter-long fence to enclose a rectangle on one side against the wall. The ratio of length to width is 2 to 1, what is the maximum area of the rectangle in square meters?
王叔叔想用24米长的篱笆，在一边靠墙的地方围一个长方形．长和宽的比是2比1，这个长方形的面积最大是多少平方米．
<gadget id="calculator">1 + 1 + 2</gadget>
<output>4</output>

<gadget id="calculator">24 / 4</gadget>
<output>6</output>

<gadget id="calculator">6 * 2 * 6</gadget>
<output>72</output>

<result>72</result>