The base of a parallelogram is 21 decimeters and the height is twice the base. What is the area of the parallelogram in square meters?
一个平行四边形的底是21分米，高是底的2倍，平行四边形的面积是多少平方米．
<gadget id="calculator">21 * 2</gadget>
<output>42</output>

<gadget id="calculator">42 / 100</gadget>
<output>21/50 = around 0.42</output>

<gadget id="calculator">21 * (21/50)</gadget>
<output>441/50 = around 8.82</output>

<result>441/50 = around 8.82</result>