A rectangle and a square have the same perimeter. If the length of the rectangle is 12 cm and the width is 6 cm, what is the area of the square in square centimeters?
一个长方形和一个正方形的周长相等，已知长方形的长是12厘米，宽是6厘米，则正方形的面积是多少平方厘米．
<gadget id="calculator">12 + 6</gadget>
<output>18</output>

<gadget id="calculator">2 / 4</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">18 * (1/2)</gadget>
<output>9</output>

<gadget id="calculator">9 * 9</gadget>
<output>81</output>

<result>81</result>