A threshing floor is 65 meters long and 50 meters wide. After expansion, the length increases by 15 meters and the width increases by 10 meters. How much does the area of the threshing floor increase?
一个打谷场长65米，宽50米，扩建后长增加15米，宽增加10米，算一算打谷场的面积增加了多少？
<gadget id="calculator">65 + 15</gadget>
<output>80</output>

<gadget id="calculator">50 + 10</gadget>
<output>60</output>

<gadget id="calculator">80 * 60</gadget>
<output>4_800</output>

<gadget id="calculator">65 * 50</gadget>
<output>3_250</output>

<gadget id="calculator">4_800 - 3_250</gadget>
<output>1_550</output>

<result>1_550</result>