If the figure is a hexagon composed of nine equilateral triangles, it is known that the side length of the smallest equilateral triangle in the middle is a, then the circumference of the enclosed hexagon is () A. 30ab. 32AC. 34ad

If the figure is a hexagon composed of nine equilateral triangles, it is known that the side length of the smallest equilateral triangle in the middle is a, then the circumference of the enclosed hexagon is () A. 30ab. 32AC. 34ad

Let the side length of the second small equilateral triangle in the lower right corner be x, then the side lengths of the remaining seven equilateral triangles are x x x + a x + a x + 2A x + 3a. According to the meaning of the question, we get: 2x = x + 3a, and the solution is: x = 3A, the circumference of the hexagon enclosed by is 3A + 3A + (3a + a) + (3a + a) + (3a + 2a) + (3a + 2a) + (3a + 3a) = 30A