Farrokh

They are independent and you are right. Thank you so much. Somtimes simple and abvious things seem more complex. Wait a moment. Now I think it is wrong. In this case the probability of not failure is 0.0189 and the probability of failure is (.5x.4x.65x.6x.55)=0.0429. It is wrong, isn't it?

Hi. I got a problem which is related to Probabilities Theory. Suppose that we have a system that consists of, for example, 5 parts a, b, c, d and e. And also we have these informations: If a fails, the system will fail with probability of 50%. If b fails, the system will fail with probability of 40%. And If c, d and e don't fail, the system won't fail with probability of 35%, 40% and 45% respectively. Now this is the question: What is the probability of the system not being failed, if a and b are failed and c, d, e, aren't. Please explain the method, too. Thank you for your help.