The base of a parallelogram is 9 cm, and the height is twice the base, what is the area of the parallelogram in cm**2.
一个平行四边形的底是9厘米，高是底的2倍，这个平行四边形的面积是多少cm**2．
<gadget id="calculator">9 / 2</gadget>
<output>9/2 = around 4.5</output>

<gadget id="calculator">(9/2) * 9</gadget>
<output>81/2 = around 40.5</output>

<result>81/2 = around 40.5</result>