A trapezoidal fish pond has an upper bottom of 400 meters, a lower bottom of 500 meters, and a height of 100 meters. If 1,200 fish are raised per hectare of water surface, how many fish will be raised in this fish pond?
一个梯形鱼池，上底400米，下底500米，高100米，如果每公顷水面养鱼1200尾，这个鱼池共养鱼多少尾？
<gadget id="calculator">400 + 500</gadget>
<output>900</output>

<gadget id="calculator">100 / 2 / 10_000</gadget>
<output>1/200 = around 0.005</output>

<gadget id="calculator">1_200 * 900 * (1/200)</gadget>
<output>5_400</output>

<result>5_400</result>