If the area of a triangle is 15 square centimeters, what is the area of a parallelogram with the same base and height?
一个三角形的面积是15平方厘米，和它等底等高的平行四边形的面积是多少．
<gadget id="calculator">15 * 2</gadget>
<output>30</output>

<result>30</result>