The wall of a gymnasium is circular. Xiaohua walks around the wall, a total of 628 steps. Each step of Xiaohua is about 0.5m long. What is the approximate area of the gymnasium?
一座体育馆的围墙是圆形的，小华沿围墙走了一圈，一共是628步，小华每步长约0.5m，这座体育馆的占地面积大约是多少？
<gadget id="calculator">0.5 * 628</gadget>
<output>314</output>

<gadget id="calculator">314 / 3.14 / 2</gadget>
<output>50</output>

<gadget id="calculator">50 ** 2</gadget>
<output>2_500</output>

<gadget id="calculator">3.14 * 2_500</gadget>
<output>7_850</output>

<result>7_850</result>