Cut out the largest square from a piece of rectangular paper 9 cm wide and 5 cm wide. What is the perimeter of this square in cm?
用一张9厘米、宽5厘米的长方形纸剪一个最大的正方形，这个正方形的周长是多少厘米
<gadget id="calculator">5 * 4</gadget>
<output>20</output>

<result>20</result>