# Probability with two six-sided dice

• Oct 23rd 2009, 03:21 PM
nautica17
Probability with two six-sided dice
I have a question about probability with two dice. Let's say that I roll two six sided dice. What would be the probability that my total is equal to four?

Here is my thinking of possible outcomes:

{3,1}, {1,3}, {2,2}

I'm wondering if the {2,2} combo has to be repeated twice. So then would the probability be 1/12 or 1/9?
• Oct 23rd 2009, 05:43 PM
Prove It
Quote:

Originally Posted by nautica17
I have a question about probability with two dice. Let's say that I roll two six sided dice. What would be the probability that my total is equal to four?

Here is my thinking of possible outcomes:

{3,1}, {1,3}, {2,2}

I'm wondering if the {2,2} combo has to be repeated twice. So then would the probability be 1/12 or 1/9?

Draw a two way table, with the possible outcomes for the first roll along your horizontal axis, and the possible outcomes for the second roll along your vertical axis.

Then fill in the table with the sums of the two rolls. This will be your sample space.

See attachment. Can you go from here?
• Oct 23rd 2009, 06:16 PM
mr fantastic
Quote:

Originally Posted by Prove It
Draw a two way table, with the possible outcomes for the first roll along your horizontal axis, and the possible outcomes for the second roll along your vertical axis.

Then fill in the table with the sums of the two rolls. This will be your sample space.

See attachment. Can you go from here?

I usually use a dice table like this one: Dice table