In a trapezoidal wheat field, the upper base is 190 meters, the lower base is 450 meters, and the height is 150 meters. A total of 16.8 tons of wheat is harvested. How many tons of wheat are harvested per hectare on average?
一块梯形麦田，上底是190米，下底是450米，高150米，共收小麦16.8吨，平均每公顷收小麦多少吨？
<gadget id="calculator">190 + 450</gadget>
<output>640</output>

<gadget id="calculator">150 / 2 / 10_000</gadget>
<output>3/400 = around 0.0075</output>

<gadget id="calculator">640 * (3/400)</gadget>
<output>24/5 = around 4.8</output>

<gadget id="calculator">16.8 / (24/5)</gadget>
<output>3.5</output>

<result>3.5</result>