From a rectangular card with a length of 15 cm and a width of 10 cm, cut out the largest square. What is the perimeter of this square?
一张长为15厘米，宽为10厘米的长方形卡片，剪下一个最大的正方形，这个正方形的周长是多少？
<gadget id="calculator">10 * 4</gadget>
<output>40</output>

<result>40</result>