00:01
For this problem, we are told that there is a 20 % chance of snow today and a 20 % chance of snow tomorrow.
00:06
Assuming that the event it snows today is independent of the event that it snows tomorrow, we are to draw a tree diagram showing the probabilities of all outcomes, and we are asked, what is the probability that it will snow by the end of tomorrow? so we first split off, i'll call it event s1 and event s1 prime for does it snow today, and then call it s2 and s2 prime for does it snow tomorrow.
00:30
So let's see here.
00:34
We'd have 20 % chance of snow today, so we have 0 .2, 20 % chance of snow tomorrow, so we have another 0 .2.
00:41
And then the s2 prime and s1 prime will be 0 .8 for each of them.
00:51
Then we can figure out the probabilities of all possible outcomes.
00:56
So for s1 and s2 to occur, we'd have probability 0 .04.
01:02
So that's two days of snow in a row.
01:05
For s1 and then s2 prime, so it snows today but not tomorrow, it's probability 0 .16...