Use a piece of paper with a length of 40 cm and a width of 30 cm to form the largest square. What is the perimeter of the square in cm?
用一张长40厘米，宽30厘米的纸，做成一个最大的正方形，这个正方形的周长是多少厘米？
<gadget id="calculator">30 * 4</gadget>
<output>120</output>

<result>120</result>