The time to fix a TV,is an exponential random variable with parameter $\lambda=\frac{1}{2}$.What is the probability that a fix take more than 2 hours?

Question

I got the following question to solve:

The time to fix a TV in hours, is an exponential random variable with parameter $\lambda = \frac{1}{2}$. What is the probability that a fix take more than 2 hours?

The answer is $e^{-1}$. I tried to use some formulas but with no success;

How should such question to be solved?

Thanks in advance.

Answer 1

You look up the Cumulative Distribution Function of the distribution. $CDF(x)$ is the chance the repair takes less than $x$ time. To get the chance it takes more, subtract from $1$.