# Quick Question about Math : Diagrams

1. Jan 27, 2016

### masterchiefo

1. The problem statement, all variables and given/known data
A system , which comprises three components (A , B and C ) , the system fails if the first component ( A) has failed or if the other two fail simultaneously. It will be assumed that all components operate independently.

Question: Choose from the following diagrams that best fits this description :
http://i.imgur.com/JRFGFkS.png

2. Relevant equations

3. The attempt at a solution
http://i.imgur.com/B6Op3ym.png

Just want to make sure I'm correct.

Thanks.

2. Jan 27, 2016

### PeroK

That's not how I would interpret those diagrams. What's your thinking?

3. Jan 27, 2016

### Ray Vickson

You should refer to the conventions used in your course notes and/or textbook. The "usual" interpretation of such diagrams is that when the component is operational a signal (or whatever) gets through that branch successfully. You seem to be using the opposite convention in which you look at "failure" rather than "success", but as I said, you should double-check the conventions used in your course. Depending on the interpretation, the answers will be completely different.

4. Jan 27, 2016

### masterchiefo

Edit: looking at my note books.

Last edited: Jan 27, 2016
5. Jan 27, 2016

### masterchiefo

I was interpreting it wrong:

http://i.imgur.com/ynKj6x7.png

do you guys agree?

6. Jan 27, 2016

### PeroK

I don't think "or" is the key word. I think the key words are system and failure. You first need to define what it means for your system to fail.

In the diagram you chose, describe the state of the system as it is. And then describe the state of the system if A has failed.

What is the system doing?

7. Jan 27, 2016

### PeroK

Yes. Think of an IT system with A, B and C as front-end components. When is your system down?

8. Jan 27, 2016

### Ray Vickson

I do, yes (assuming that "component works" = "signal gets through").