Answer:
60
Explanation:
In a rhombus, all sides are equal in length. Let x be the length of each side of the rhombus.
Since AC and BD are diagonals of the rhombus, they intersect at their midpoint, which we can call O. Therefore, AO = CO = 9 and BO = DO = 12.
Using the Pythagorean theorem, we can find the length of AB:
AB^2 = AO^2 + BO^2
AB^2 = 9^2 + 12^2
AB^2 = 225
AB = 15
Therefore, the perimeter of the rhombus is:
4x = 4(15) = 60
So the perimeter of ABCD is 60 units.