The width of the sports field is 30 meters and the circumference is 280 meters. What is its area in square meters?
体育活动场的宽是30米，周长是280米，它的面积是多少平方米？
<gadget id="calculator">280 / 2</gadget>
<output>140</output>

<gadget id="calculator">140 - 30</gadget>
<output>110</output>

<gadget id="calculator">110 * 30</gadget>
<output>3_300</output>

<result>3_300</result>