The diameter of a circular roller skating rink is 20 meters. After the expansion, the radius increases by 10 meters. How many square meters does the area of the roller skating rink increase after the expansion?
一个圆形旱冰场的直径是20米，扩建后半径增加了10米，扩建后的旱冰场面积增加了多少平方米？
<gadget id="calculator">20 / 2</gadget>
<output>10</output>

<gadget id="calculator">10 + 10</gadget>
<output>20</output>

<gadget id="calculator">20 ** 2</gadget>
<output>400</output>

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

<gadget id="calculator">400 - 100</gadget>
<output>300</output>

<gadget id="calculator">3.14 * 300</gadget>
<output>942</output>

<result>942</result>