Use a rectangular board with a length of 16 decimeters and a width of 4 decimeters to make a square with the same area and the largest size, and there is no residue, what is the side length of the square?
用一块长16分米、宽4分米的长方形木板做一个面积相等、最大的正方形，且没有剩余，则正方形的边长是多少？
<result>8</result>