A triangular vegetable field has a base of 280 meters and a height of 50 meters. How many hectares is this vegetable field?
一块三角形菜地，底是280米，高是50米．这块菜地的面积是多少公顷？
<gadget id="calculator">50 / 2 / 10_000</gadget>
<output>1/400 = around 0.0025</output>

<gadget id="calculator">280 * (1/400)</gadget>
<output>7/10 = around 0.7</output>

<result>7/10 = around 0.7</result>