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I recently lost my notes on this matter, so I hope someone can fill in the gaps in my memory.

The problem I am working on is the following:

For one ticket window, the waiting time for one people satisfies an exponential distribution λe-λt and expected waiting time is 4 min.

a. What’s the probability of the waiting time less than 7 min for 2 persons?

b. What’s the probability of the waiting time longer than 165 min for 36 persons?

As far as my memory goes:

a) P(X>7) = 1 - (1-e^(-0,25*7)) = ... -> for one person

However I thought the amount of people influences the result, but I can't remember how.

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# Exponential distribution problem

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