1. The problem statement, all variables and given/known data Question: A system consists of 7 equal reliable components having the following configuration with each component has a reliability of 0.9. Find the reliability of the system. 2. Relevant equations I was taught (and only been taught) with the calculations to obtain reliability of a system with its components arranged in either in series or in parallel. However, I have real trouble in solving these kinds of complex configuration. For series: Rs = R1R2...Rn For parallel: Rs = 1-(1-R1)(1-R2)...(1-Rn) 3. The attempt at a solution I have search through the internet and realized that this can be solved with the solution used for bridge structure. I tried to mimic the way the solution from the resource (Reliability Engineering: Theory and Practice, by Alessandro Birolini) found (but with only 5 component instead of 7) and come to this: The first picture showing the reliability of the system with the center component not fail, and the second picture is when the center component has fail. (component number order: 1 to 6, from top left, clockwise; center = 7) Then, Rs=R7(R1+R6-R1R6)(R2+R5-R2R5)(R3+R4-R3R4) + (1-R7)(R1R2R3+R4R5R6-R1R2R3R4R5R6) This solution doesn't lead to the answer (0.9575). I tried using Binomial method by considering all sort of possibility but still no help (duh, obviously), so can anyone enlighten me?