The skating rink was originally 60 meters long and 30 meters wide. After the expansion, the length increased by 30 meters and the width increased by 20 meters. How many square meters has been added after the expansion?
溜冰场原来长60米，宽30米，扩建后长增加了30米，宽增加了20米．扩建后增加了多少平方米？
<gadget id="calculator">60 + 30</gadget>
<output>90</output>

<gadget id="calculator">30 + 20</gadget>
<output>50</output>

<gadget id="calculator">90 * 50</gadget>
<output>4_500</output>

<gadget id="calculator">60 * 30</gadget>
<output>1_800</output>

<gadget id="calculator">4_500 - 1_800</gadget>
<output>2_700</output>

<result>2_700</result>