A trapezoidal land, the upper base is 120 meters, the lower base is 160 meters, and the height is 75 meters. How many hectares is this land?
一块梯形地，上底120米，下底160米，高75米．这块地有多少公顷？
<gadget id="calculator">120 + 160</gadget>
<output>280</output>

<gadget id="calculator">75 / 2 / 10_000</gadget>
<output>3/800 = around 0.00375</output>

<gadget id="calculator">280 * (3/800)</gadget>
<output>21/20 = around 1.05</output>

<result>21/20 = around 1.05</result>