A trapezoidal vegetable field is 80 meters long at the top, 100 meters long at the bottom, and 40 meters high. 75% of them grow Chinese cabbage. How many hectares are used to grow Chinese cabbage?
一个梯形菜地，上底长80米，下底长100米，高40米．其中的75%种白菜，种白菜的面积是多少公顷？
<gadget id="calculator">80 + 100</gadget>
<output>180</output>

<gadget id="calculator">40 / 2</gadget>
<output>20</output>

<gadget id="calculator">75 / 100</gadget>
<output>3/4 = around 0.75</output>

<gadget id="calculator">180 * 20 * (3/4)</gadget>
<output>2_700</output>

<result>2_700</result>