If a triangle has a base of 20 cm and a height of half the base, what is the area of the triangle in square centimeters?
一个三角形，它的底是20厘米，高是底的一半，这个三角形的面积是多少平方厘米．
<gadget id="calculator">20 / 2</gadget>
<output>10</output>

<gadget id="calculator">10 / 2</gadget>
<output>5</output>

<gadget id="calculator">20 * 5</gadget>
<output>100</output>

<result>100</result>