A trapezoidal vegetable field, the upper base is 30 meters long, and the lower base is reduced by 10 meters to become a parallelogram with an area of 1500 square meters. What is the area of the original trapezoid?
一个梯形菜地，上底长30米，下底减少10米就变成一个面积为1500平方米的平行四边形，原来梯形面积是多少？
<gadget id="calculator">30 + 10</gadget>
<output>40</output>

<gadget id="calculator">30 + 40</gadget>
<output>70</output>

<gadget id="calculator">1_500 / 30</gadget>
<output>50</output>

<gadget id="calculator">50 / 2</gadget>
<output>25</output>

<gadget id="calculator">70 * 25</gadget>
<output>1_750</output>

<result>1_750</result>