00:01
So in this question we're told that the number of days that elapsed between the beginning of a calendar year and the moment a high -risk driver is involved in an accident is exponentially distributed.
00:09
So let's call it x and let's say that it's exponentially distributed with the parameter lambda.
00:15
Now we're told that the probability of being involved in an accident during the first 50 days is 30%.
00:21
So the probability x is less than or equal to 50 is 30%.
00:28
So 0 .30.
00:32
So now we can use that to find out what language.
00:34
So this relationship tells us that f x is lambda e to the minus lambda x.
00:44
So the probability that x is less than or equal to some number x, it's the integral from 0 to x, lambda e to the minus lambda x d x, which is minus e to the minus lambda x, evaluated between 0 and x, which is 1 minus e to the minus lambda x.
01:05
Now we're told that the probability that x is less than or equal to 50, is 0 .30 and that's 1 minus e to the minus 50 lambda.
01:16
So e to the minus 50 lambda is 0 .7, 1 minus 0 .3...