Answer: 120 ft
Explanation: The length of 30 feet consists of two shorter sides of the triangles. Since we know that the triangles are the same size then one side must be half of the total.
Short side in 30-60-90: 15ft
The outer edges of the rhombus are the hypotenuses of the triangles. In all 30-60-90 the hypotenuse is twice as long as the shortest side.
One edge of rhombus: 30ft
30 x 4 = 120