The area of a rectangular park is 12 hectares. Expand the length of the park to three times its original size, and keep the width unchanged. What is the area of the park after the expansion?
一个长方形公园的面积是12公顷．将这个公园的长扩大到原来的3倍，宽不变．扩建后公园的面积是多少？
<gadget id="calculator">12 * 3</gadget>
<output>36</output>

<result>36</result>