1. The problem statement, all variables and given/known data a) Find the probability that a molecule will travel a distance at least equal to the mean free path before its next collision. b)After what distance of travel since the last collision is the probability of having suffered the next collision equal to 1/2? 2. Relevant equations Exponential probability distribution f(r) = Ae-r/[tex]\lambda[/tex] where A = a constant, [tex]\lambda[/tex] = mean free path 3. The attempt at a solution P = Integral (limits [tex]\lambda[/tex] to [tex]\infty[/tex])f(r) dr / Integral (limits 0 to [tex]\infty[/tex]) f(r) dr I will do the calculations of both parts but not sure about the probability. I have found probability by number of molecules with distance between collision greater than lambda / total number of molecules. Is this probability correct?