A rectangular vegetable garden is enclosed by a bamboo fence with a length of 36 cm. What is the maximum area of the enclosed vegetable garden?
用长为36厘米的竹篱笆围成一个长方形的菜园，围成菜园的最大面积是多少．
<gadget id="calculator">36 / 4</gadget>
<output>9</output>

<gadget id="calculator">9 * 9</gadget>
<output>81</output>

<result>81</result>