There are a square and a rectangle with a perimeter of 40 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40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">10 * 10</gadget>
<output>100</output>

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

<gadget id="calculator">40 / 2 / 4</gadget>
<output>5</output>

<gadget id="calculator">5 * 3</gadget>
<output>15</output>

<gadget id="calculator">15 * 5</gadget>
<output>75</output>

<gadget id="calculator">100 - 75</gadget>
<output>25</output>

<result>25</result>