Answer to Question #200693 in Statistics and Probability for Bazin

Question

Interarrival time of mails are exponentially with a mean 10 minutes what is the probability 5 mails arrive in 20 minutes?

Answer 1

Given $\lambda=1/10=0.1$

$$P(x\leq\dfrac{20}{5})=1-e^{0.1(4)}\approx0.3297$$

The probability 5 mails arrive in 20 minutesn is $0.3297.$