A triangle and a parallelogram have the same height and the same area, and the base of the parallelogram is 20 cm. What is the length of the base of the triangle?
一个三角形和一个平行四边形的高相等，面积也相等，平行四边形的底是20厘米，那么这个三角形的底边长多少．
<gadget id="calculator">20 * 2</gadget>
<output>40</output>

<result>40</result>