On a drawing with a scale of 1:400, a rectangular vegetable field is measured to be 4 cm long and 2.5 cm wide. What is the actual area of this vegetable field?
在比例尺是1：400的图纸上，量得一块长方形的菜地长是4厘米，宽是2.5厘米，这块菜地的实际面积是多少？
<gadget id="calculator">1 / 400</gadget>
<output>1/400 = around 0.0025</output>

<gadget id="calculator">4 / (1/400) / 100</gadget>
<output>16</output>

<gadget id="calculator">2.5 / (1/400) / 100</gadget>
<output>10</output>

<gadget id="calculator">16 * 10 * 10</gadget>
<output>1_600</output>

<result>1_600</result>