A circular flower bed has an outer diameter of 200 meters and an inner radius of 80 meters. How many square meters is the area of the ring flower bed?
一个环形花坛的外直径200米，内半径80米．环形花坛的面积多少平方米？
<gadget id="calculator">200 / 2</gadget>
<output>100</output>

<gadget id="calculator">100 ** 2</gadget>
<output>10_000</output>

<gadget id="calculator">3.14 * 10_000</gadget>
<output>31_400</output>

<gadget id="calculator">80 ** 2</gadget>
<output>6_400</output>

<gadget id="calculator">3.14 * 6_400</gadget>
<output>20_096</output>

<gadget id="calculator">31_400 - 20_096</gadget>
<output>11_304</output>

<result>11_304</result>