00:01
All right, so the probability of b given a is going to be a probability of b and a over the probability of a.
00:13
So the probability of a is going to be 8 choose 6 and that's going to be times p to the power 6 times 1 minus p to the power 2.
00:34
And then for a and b, we also know, well, we know that this is going to be p because b is the event of the ninth toss results in heads.
00:49
So that's just going to give us p and then that's going to be times 8 choose 6 times probability of 6 times 1 minus p squared.
01:04
Because that's the first eight tosses.
01:15
Okay, so in this case we can simplify this a little bit, cancel out terms.
01:20
So in this case, this would just be p.
01:27
So therefore, the probability that the ninth toss heads results in heads, given that there are exactly six tosses in the first eight tosses, is just p.
01:38
So for 2, we want three heads in the first four tosses and two heads in the last three.
01:45
So press our answer in terms of p.
01:48
So probability of three heads and four tosses is just going to be 4 choose 3 times p cubed 1 minus p.
02:10
And then two heads and three tosses is going to be the same.
02:15
Or i'm sorry, yeah, two heads and last three tosses.
02:21
So two heads and three tosses, 3 choose 2, p squared 1 minus p.
02:32
So since these events are independent, we're going to have basically probability of event 1 and event 2.
02:46
So we'll just be multiplying the two events.
02:54
So we're going to get 4 choose 3 times p.
03:00
Well, 4 choose 3 times 3 choose 2 times this would be p to the fifth and times 1 minus p squared.
03:19
For 3, we want four heads in the first seven tosses.
03:24
Also given that there's four heads in the first seven tosses, find the probability that the second heads occurs on the fourth toss.
03:37
So in that case, that's going to be the probability of e given f.
03:44
So we can write that as the probability of f given e times the probability of e and then divide that by the probability of f...