Use 25 small squares with a side length of 1 decimeter to form a large square. What is the perimeter of this large square?
用25个边长为1分米的小正方形，拼成一个大正方形，这个大正方形的周长是多少分米．
<gadget id="calculator">1 * 5</gadget>
<output>5</output>

<gadget id="calculator">5 * 4</gadget>
<output>20</output>

<result>20</result>