# Probability Density Function Help

1. Oct 7, 2006

### Mesmer

Probability Density Function....Help

The probabiltiy density function of the time to failure of an electric component in hours is $$f(x)=e^{(-x/3000)/3000}$$ for x > 0 and f(x) = 0 for $$x \leq 0$$ determine the probability that

a) A component last more than 1000 hours before failure
I know how to solve this part. All I have to to is integrate the given function from [1000, infinity].

But how do determine the number of hours at wich 10% of all the components have failed? I don't know what interval I should integrate over. Any Ideas?

Last edited: Oct 7, 2006
2. Oct 8, 2006

### 0rthodontist

If F(x) is the probability that a component has failed by time x, you are looking for when F(x) = .10. Can you solve that?

3. Oct 8, 2006

### Mesmer

yes I can. thank you!

4. Oct 8, 2006

### Mesmer

when I solve it as you state that is no the answer.
any other ideas?