A triangular green space has a base length of 30 meters and a height of 20 meters. Find the area of this green space.
一块三角形绿地底长30米，高20米，求这块绿地的面积．
<gadget id="calculator">20 / 2</gadget>
<output>10</output>

<gadget id="calculator">30 * 10</gadget>
<output>300</output>

<result>300</result>