A parallelogram wheat field has a base of 140 meters and a height of 30 meters. How many hectares does this wheat field cover?
一块平行四边形的麦田，底是140米，高为30米，这块麦田的占地面积是多少公顷？
<gadget id="calculator">140 * 30</gadget>
<output>4_200</output>

<gadget id="calculator">4_200 / 10_000</gadget>
<output>21/50 = around 0.42</output>

<result>21/50 = around 0.42</result>