The surface of a fish pond is approximately trapezoidal, with an upper bottom of 780 meters, a lower bottom of 540 meters, and a height of 120 meters. How many hectares does this fish pond have?
一个养鱼池的池面近似于一个梯形，上底780米，下底540米，高120米，这个养鱼池水面大约有多少公顷？
<gadget id="calculator">780 + 540</gadget>
<output>1_320</output>

<gadget id="calculator">120 / 2 / 10_000</gadget>
<output>3/500 = around 0.006</output>

<gadget id="calculator">1_320 * (3/500)</gadget>
<output>198/25 = around 7.92</output>

<result>198/25 = around 7.92</result>