The school has a playground with a length of 150 meters and a width of 30 meters. Now it is necessary to expand the playground. The width remains the same and the length is increased by 20 meters. How many square meters will the playground area increase?
学校有一块长150米，宽30米的操场，现在要扩建操场，宽不变，长增加20米，操场面积增加多少平方米？
<gadget id="calculator">20 * 30</gadget>
<output>600</output>

<result>600</result>