On a drawing with a scale of 1:500, the side length of a square lawn is measured to be 4 cm. What is the actual area of the lawn?
在比例尺是1：500的图纸上，量得一个正方形草坪的边长是4厘米．这个草坪的实际面积是多少．
<gadget id="calculator">1 / 500</gadget>
<output>1/500 = around 0.002</output>

<gadget id="calculator">4 / (1/500) / 100</gadget>
<output>20</output>

<gadget id="calculator">20 * 20</gadget>
<output>400</output>

<result>400</result>