rectangle has a width of 3 cm and a length three times its width. What is the perimeter of this rectangle in centimeters?
一个长方形的宽是3厘米，长是宽的3倍．这个长方形的周长是多少厘米？
<gadget id="calculator">3 * 3</gadget>
<output>9</output>

<gadget id="calculator">3 + 9</gadget>
<output>12</output>

<gadget id="calculator">12 * 2</gadget>
<output>24</output>

<result>24</result>