A rectangular piece of paper is 40 cm long and 20 cm wide. Cut out the largest triangle from this paper. What is the area of this triangle in square centimeters?
一个长方形的纸，长是40厘米，宽是20厘米，从这张纸上剪下一个最大的三角形，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">40 * 10</gadget>
<output>400</output>

<result>400</result>