# Math Help - Help with Probability

1. ## Help with Probability

Need some help to solve this one. Don't understand how I should start and so ...

2. Originally Posted by kevin3000
Need some help to solve this one. Don't understand how I should start and so ...

Have you been taught Markov Chains? If not, then you can draw a tree diagram:

Note that Monday is dry so the first two branches are dry (0.8) and rainy (0.2). Now draw the next set of branches and use the given information to label their probability.

Now use the tree diagram to get the answer. I get (0.8)(0.2) + (0.2)(0.6) = .... but you better double check because I'm terrible at these things.

3. Originally Posted by mr fantastic
Have you been taught Markov Chains? If not, then you can draw a tree diagram:

Note that Monday is dry so the first two branches are dry (0.8) and rainy (0.2). Now draw the next set of branches and use the given information to label their probability.

Now use the tree diagram to get the answer. I get (0.8)(0.2) + (0.2)(0.6) = .... but you better double check because I'm terrible at these things.
I don't understand 100% can someone further explain

4. Originally Posted by kevin3000
I don't understand 100% can someone further explain
As there are only 2 days, it's probably easier to list all possibilities
Let p denote the probability of dry/rainy
Mon Dry: p=1

Tue Dry: p=0.8
Wed Dry: p=0.8*0.8
Wed Rainy: p=0.8*0.2

Tue Rainy: p=0.2
Wed Dry: p=0.2*0.4
Wed Rainy: p=0.2*0.6

hence simply add up all the probabilities that makes Wed a rainy day

5. Originally Posted by kevin3000
I don't understand 100% can someone further explain
It would help if you said which part of the 100% you didn't understand. Are you saying that you don't know what a tree diagram is?