# Exponential Distribution Problem

#### cachapa69

##### New Member
Hi!

I am doing a problem using the exponential distribution function, but I'm having trouble understanding iii.

There was a typo and the answer for iii is actually e^-4lambda, but I still don't understand how i'd get there. I think I have to use conditional probability but even then I'm not sure how I'd set it up.

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#### obh

##### Active Member
Hi Cachapa,

This is the memoryless property of the exponential distribution.

A long time since I used conditional probability if I remember correctly ...
Please try to calculate, and let me know what you get, and how you get it.
A - 8 minutes without event
B - 4 minutes without event

P(A|B)=P(A and B)/P(B)