In a trapezoidal rice field, the upper base is 150 meters, the lower base is 300 meters, and the height is 80 meters. There are 12.6 tons of rice harvested in total. How many tons of rice are harvested per hectare on average?
一块梯形稻田，上底150米，下底300米，高80米，共收稻谷12.6吨，平均每公顷收稻谷多少吨？
<gadget id="calculator">150 + 300</gadget>
<output>450</output>

<gadget id="calculator">80 / 2 / 10_000</gadget>
<output>1/250 = around 0.004</output>

<gadget id="calculator">450 * (1/250)</gadget>
<output>9/5 = around 1.8</output>

<gadget id="calculator">12.6 / (9/5)</gadget>
<output>7</output>

<result>7</result>