(2/5) hectare = how many square meters.
(2/5)公顷=多少平方米．
<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">(2/5) * 10_000</gadget>
<output>4_000</output>

<result>4_000</result>