Use a square wire frame with a perimeter of 80 cm to enclose it into a rectangle whose length is three times its width. Find the area of the rectangle formed.
用一个周长是80厘米的正方形铁丝框，改围成长方形，长是宽的3倍，求围成的长方形的面积．
<gadget id="calculator">3 + 1</gadget>
<output>4</output>

<gadget id="calculator">80 / 2 / 4</gadget>
<output>10</output>

<gadget id="calculator">10 * 3</gadget>
<output>30</output>

<gadget id="calculator">30 * 10</gadget>
<output>300</output>

<result>300</result>