# Thread: Quick Dice /Probability Question

1. ## Quick Dice /Probability Question

This one has my head spinning, could someone help me out on the following dice problem? I'm having difficulty figuring out whether or not this is a permutation or combination question.

Thanks in advance!

Suppose two 6-sided dice are rolled.

What is the probability that the sum is divisible by 5 or exactly 12?

2. ## Re: Quick Dice /Probability Question

List all the possible outcomes, how many is there?

What are the probabilites for rolling a 5,10 & 12?

3. ## Re: Quick Dice /Probability Question

Originally Posted by pickslides
List all the possible outcomes, how many is there?

What are the probabilites for rolling a 5,10 & 12?
Oh now I feel dumb,

With 36 possible outcomes, I suppose it would be as simple as 3/36 = 0.0833. D'oh! Thanks very much for the nudge in the right direction.

This problem may be slightly more complex, as it involves finding the mean of a discreet probability model,

Suppose you roll a 6-sided die. If you roll a 2 you make $2, if you roll a 6 you make$3 and if you roll any other number you pay $0.5. How much money should you expect to make on average? I know the formula for finding the mean is as simple as adding the various outcomes times their respective probabilities. But I'm unsure as to how I am supposed to plug in the data from the question. Any ideas? 4. ## Re: Quick Dice /Probability Question Originally Posted by Danny09 With 36 possible outcomes, I suppose it would be as simple as 3/36 = 0.0833. D'oh! Thanks very much for the nudge in the right direction. Maybe there is more than 3, we have (1,4),(2,3),(3,2),(4,1),(4,6),(6,6),(6,4),(6,6) 5. ## Re: Quick Dice /Probability Question Originally Posted by Danny09 Suppose you roll a 6-sided die. If you roll a 2 you make$2, if you roll a 6 you make $3 and if you roll any other number you pay$0.5. How much money should you expect to make on average?

I know the formula for finding the mean is as simple as adding the various outcomes times their respective probabilities. But I'm unsure as to how I am supposed to plug in the data from the question. Any ideas?
Expected Value would be 2*(1/6)+3*(1/6)-0.5*(4/6) can you see why?