The width of the rectangular vegetable field is 4.5 meters and the area is 81 square meters. What is the length of the vegetable field in meters?
长方形菜地的宽是4.5米，面积是81平方米，菜地的长是多少米？
<gadget id="calculator">81 / 4.5</gadget>
<output>18</output>

<result>18</result>