A principal square playground covers an area of 2,800 square meters. Due to expansion, the width needs to be increased from 40 meters to 50 meters, and the length remains unchanged. How many square meters has the expanded playground area increased compared to the original?
某校长方形操场面积2800平方米，因扩建，要把宽从40米增加到50米，长不变．扩建后的操场面积比原来增加多少平方米？
<gadget id="calculator">2_800 / 40</gadget>
<output>70</output>

<gadget id="calculator">50 - 40</gadget>
<output>10</output>

<gadget id="calculator">70 * 10</gadget>
<output>700</output>

<result>700</result>