A triangle and a parallelogram have the same area and height, the base of the triangle is 4.2dm, what is the base of the parallelogram.
一个三角形和一个平行四边形面积相等，高也相等，三角形的底是4.2dm，平行四边形的底是多少．
<gadget id="calculator">4.2 / 2</gadget>
<output>2.1</output>

<result>2.1</result>