- #1
skrat
- 748
- 8
Homework Statement
Waiting time in a restaurant is exponentially distributed variable, with average of 4 minutes. What is the probability, that a student will in at least 4 out of 6 days get his meal in less than 3 minutes?
Homework Equations
The Attempt at a Solution
If I understand correctly I could say that ##f(t)=e^{-\lambda t}##, meaning ##P(t<3)=\int_{0}^{3}\omega (t)dt=\int_{0}^{3}(\frac{f(t)}{dt})dt=\int_{0}^{3}\lambda e^{-\lambda t}dt##
Ok? This is now probability that a student will get his meal in less than 3 minutes, so the probability that it would take longer is ##1-P(t<3)## and the final result should be something like ##\sum_{i=4}^{6}\begin{pmatrix}
6\\
i
\end{pmatrix}p^{i}(1-p)^{6-i}##
Does this sound right? How do I determine ##\lambda##?
Homework Statement
Elapsed time until a device suddenly stops working is exponentially distributed with median 4h. Calculate the probability, that the device will work at least for 5 hours!
Homework Equations
The Attempt at a Solution
Very different as before, but still have no idea how to get ##\lambda##?