The area of the lawn is 180 square meters. The length of this rectangular lawn is expanded to 4 times its original size, and the width remains unchanged. What is the area of the lawn after expansion?
草坪面积是180平方米，将这个长方形的草坪的长扩大到原来的4倍，宽不变．扩建后草坪的面积是多少平方米？
<gadget id="calculator">180 * 4</gadget>
<output>720</output>

<result>720</result>