The base of a triangle is 10 decimeters, and the height is 8 decimeters. If the base is doubled and the height is reduced to 1/2, what is the area of the triangle?
一个三角形的底是10分米，高是8分米，若把底扩大为原来的2倍，高缩小为原来的(1/2)，则这个三角形的面积为多少平方分米．
<gadget id="calculator">10 * 2</gadget>
<output>20</output>

<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">8 * (1/2)</gadget>
<output>4</output>

<gadget id="calculator">20 * 4 * (1/2)</gadget>
<output>40</output>

<result>40</result>