A triangle and a parallelogram have the same height and base. If the area of the triangle is 15 square decimeters, what is the area of the parallelogram?
一个三角形和一个平行四边形的高相等，底也相等，如果三角形的面积是15平方分米，则平行四边形的面积是多少平方分米．
<gadget id="calculator">15 * 2</gadget>
<output>30</output>

<result>30</result>