00:01
This is a probability question we have here.
00:03
And the probability of the pass, so the probabilities of the pass that was given as, which is 0 .7, so i can denote this probability as p.
00:13
And the probability of fail, which is equal to 1 minus 0 .7, which is 0 .3, i'm going to denote this by q.
00:23
And so what i'm going to do for the first one, so the student passed the written exam.
00:30
Written test in the third try.
00:32
So the probability of pass in third try.
00:38
So that means, so this is the try one times the try two times the three.
00:44
So if she pass in the third try, that means in the first second try she didn't pass.
00:51
So the probability of fail, which is 0 .3 times for the second one, this is 0 .3.
00:56
And for the third one, she will just pass, which is 0 .7.
01:00
Here if we just multiply this this is 63 over 1000 which would be 0 .0663 this is the probability we have for part a and what about for part b so in this case the student passed before the fourth try so let me just write student pass before before the fourth fourth try so what that means so the student just pass which is in the first try and plus the student maybe can maybe pass in the second try and the last one the student pass for the third try so the probability of getting passed for the first try which is 0 .7 plus and the next one the probability of getting in the second try which is for the first try she failed and second try she passed she passed and for this one, which is 0 .3, failed, failed.
02:09
And the last one, she passed, which is 0 .7 plus...