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Homework Help: Exponential distribution Q

  1. Jan 17, 2009 #1
    1. The problem statement, all variables and given/known data

    The distance between major cracks in the highway follows an exponential distribution with a mean of 5 miles. What is the probability that there are two major cracks in a 10 mile stretch of the highway?

    2. Relevant equations

    exponential dist: f(x) = Le(-Lx) where L = lambda (sorry i dont know latex)

    E(X) = 1/L V(X) = 1/(L)^2

    3. The attempt at a solution

    well i'm abit stumped because the probability density function for the exponential dist tells us the time to an event etc.. not the number of events. So i really don't have much of an attempt :(
  2. jcsd
  3. Jan 17, 2009 #2
    got it.. just use the poisson process.. with lambda = 2 etc.. answer is 0.2706
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