00:02
The circuit in the diagram shown works only if there's a path from the left side to the right side of it.
00:09
And the failures of the individual components, the probabilities of failure of the individual components, are shown for each component, so they're all .1.
00:19
And all devices are stated to fail independently of each other.
00:25
Now for part a, we're asked to find the probability that p1 fails.
00:28
So p1 is this subsystem here.
00:35
Now, p1 fails.
00:48
Actually, i wrote that wrong.
00:49
So the probability of p1 failing is equal to the probability that we have d fail.
01:02
So let's just call the component failing the letter that stands for the component.
01:08
So de -failing is d.
01:12
And either of a or b failing.
01:20
And since they are independent, this is equal to the probability of d failing, times the probability of a or b failing.
01:36
And the probability of a or b failing is equal to the probability of a failing plus the probability of b failing minus the probability of a and b failing.
01:52
And this is from probability theory.
02:08
The probability of a and b failing is the probability of a failing times the probability of b failing because they are independent.
02:32
Actually, they are not all 0 .1.
02:35
A and b have failure probabilities of .01.
02:38
It's always wrong about that...