A triangular flowing red flag has a base of 20 cm and a height of 30 cm. What is its area in square centimeters?
一面三角形的流动红旗底是20厘米，高是30厘米，它的面积是多少平方厘米？
<gadget id="calculator">30 / 2</gadget>
<output>15</output>

<gadget id="calculator">20 * 15</gadget>
<output>300</output>

<result>300</result>