If the area of a parallelogram is 42 square centimeters, what is the area of a triangle with the same base and height?
一个平行四边形的面积是42平方厘米，与它等底等高的三角形的面积是多少．
<gadget id="calculator">42 / 2</gadget>
<output>21</output>

<result>21</result>