The base of a triangle is 21 decimeters and the height is 10 decimeters. What is the area of the triangle?
一个三角形的底是21分米，高是10分米，这个三角形的面积是多少平方分米．
<gadget id="calculator">10 / 2</gadget>
<output>5</output>

<gadget id="calculator">21 * 5</gadget>
<output>105</output>

<result>105</result>