The area of a rectangular garden is 12 hectares. After expansion, the length will be tripled and the width will remain the same. What is the area after expansion?
一个长方形花园的面积是12公顷，扩建后，长扩大到原来的3倍，宽不变，扩建后面积是多少．
<gadget id="calculator">12 * 3</gadget>
<output>36</output>

<result>36</result>