The circumference of a circular stadium is 1570 meters, and the diameter after expansion is 1600 meters. By what percentage has the stadium been expanded?
一个圆形体育场周长是1570米，扩建后的直径是1600米，这个体育场扩建了百分之几？
<gadget id="calculator">1_600 / 2</gadget>
<output>800</output>

<gadget id="calculator">800 ** 2</gadget>
<output>640_000</output>

<gadget id="calculator">3.14 * 640_000</gadget>
<output>2_009_600</output>

<gadget id="calculator">1_570 / 3.14 / 2</gadget>
<output>250</output>

<gadget id="calculator">250 ** 2</gadget>
<output>62_500</output>

<gadget id="calculator">3.14 * 62_500</gadget>
<output>196_250</output>

<gadget id="calculator">2_009_600 - 196_250</gadget>
<output>1_813_350</output>

<gadget id="calculator">1_813_350 / 196_250</gadget>
<output>231/25 = around 9.24</output>

<gadget id="calculator">100 / 100</gadget>
<output>1</output>

<gadget id="calculator">(231/25) * 1</gadget>
<output>231/25 = around 9.24</output>

<result>231/25 = around 9.24</result>