If the base of a triangle is 18 decimeters and the height is half of the base, what is its area in square decimeters?
一个三角形的底是18分米，高是底的一半，它的面积是多少平方分米．
<gadget id="calculator">18 / 2</gadget>
<output>9</output>

<gadget id="calculator">9 / 2</gadget>
<output>9/2 = around 4.5</output>

<gadget id="calculator">18 * (9/2)</gadget>
<output>81</output>

<result>81</result>