Changhu Lake is located in Yunnan Province, 17 kilometers away from the county seat. Changhu Lake is about 3,000 meters long and 400 meters wide, with a water area of 80 hectares. The rest are two small islands. How many hectares are these two small islands?
长湖位于云南省，距县城17千米，长湖长约3000米，宽约400米，水域面积80公顷，其余是两个小岛，这两个小岛的面积是多少公顷？
<gadget id="calculator">400 / 10_000</gadget>
<output>1/25 = around 0.04</output>

<gadget id="calculator">3_000 * (1/25)</gadget>
<output>120</output>

<gadget id="calculator">120 - 80</gadget>
<output>40</output>

<result>40</result>