There is a circular flower pond in the center of the square with a diameter of 80 meters. After expansion, the diameter increases to 100 meters. How many square meters has the area of this flower pond increased?
广场中心有一个圆形花池，直径是80米，扩建后，直径增加到100米．这个花池的面积增加了多少平方米？
<gadget id="calculator">100 / 2</gadget>
<output>50</output>

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

<gadget id="calculator">80 / 2</gadget>
<output>40</output>

<gadget id="calculator">40 ** 2</gadget>
<output>1_600</output>

<gadget id="calculator">2_500 - 1_600</gadget>
<output>900</output>

<gadget id="calculator">3.14 * 900</gadget>
<output>2_826</output>

<result>2_826</result>