The base of a triangle is 20 meters and the height is 4 meters. What is its area in square meters?
一个三角形的底是20米，高4米，它的面积是多少平方米．
<gadget id="calculator">4 / 2</gadget>
<output>2</output>

<gadget id="calculator">20 * 2</gadget>
<output>40</output>

<result>40</result>