A piece of land is in the shape of an isosceles triangle. The measured circumference is 240m, one of the waists is 75m long, and the height above the base is 60m. What is the area of the land in hectares?
一块形状为等腰三角形的地，测得周长是240m，其中一条腰长75m，底边上的高为60m，这块地的面积是多少公顷？
<gadget id="calculator">75 * 2</gadget>
<output>150</output>

<gadget id="calculator">240 - 150</gadget>
<output>90</output>

<gadget id="calculator">60 / 2 / 10_000</gadget>
<output>3/1_000 = around 0.003</output>

<gadget id="calculator">90 * (3/1_000)</gadget>
<output>27/100 = around 0.27</output>

<result>27/100 = around 0.27</result>