The base of a triangle is 1500m. If the base is extended by 20m, the area will increase by 1000m**2. How many hectares is the area of the original triangle?
一个三角形底1500m，如果把底延长20m，面积就增加1000m**2，原来三角形的面积是多少公顷？
<gadget id="calculator">2 / 20 / 2 / 10_000</gadget>
<output>1/200_000 = around 0.000005</output>

<gadget id="calculator">1_500 * 1_000 * (1/200_000)</gadget>
<output>15/2 = around 7.5</output>

<result>15/2 = around 7.5</result>