There are squares and rectangles with a perimeter of 36 cm, and the length of the rectangle is 3 times the width. How many square centimeters are their areas different?
有周长都是36厘米的正方形和长方形，长方形的长是宽的3倍．它们的面积相差多少平方厘米．
<gadget id="calculator">36 / 4</gadget>
<output>9</output>

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

<gadget id="calculator">3 + 1</gadget>
<output>4</output>

<gadget id="calculator">36 / 2 / 4</gadget>
<output>9/2 = around 4.5</output>

<gadget id="calculator">(9/2) * 3</gadget>
<output>27/2 = around 13.5</output>

<gadget id="calculator">(27/2) * (9/2)</gadget>
<output>243/4 = around 60.75</output>

<gadget id="calculator">81 - (243/4)</gadget>
<output>81/4 = around 20.25</output>

<result>81/4 = around 20.25</result>