What is the area of a square field whose side length is 400 meters?
边长是400米的正方形田地，面积是多少公顷．
<gadget id="calculator">400 * 400</gadget>
<output>160_000</output>

<gadget id="calculator">160_000 / 10_000</gadget>
<output>16</output>

<result>16</result>