Cut out the largest triangle from a rectangular cardboard with a length of 40 decimeters and a width of 30 decimeters. What is the area of this triangle in square decimeters?
从一块长40分米、宽30分米的长方形纸板上剪下一个最大的三角形，这个三角形的面积是多少平方分米．
<gadget id="calculator">30 / 2</gadget>
<output>15</output>

<gadget id="calculator">40 * 15</gadget>
<output>600</output>

<result>600</result>