Melody, you said I reposted, but I get new questions every time I get one answer right. I am almost positive that they wouldn't repeat the s

Oh, I see. I wasn't paying attention.

It's ok, I trust you. (Not sure about Melody.. Haha) 

Counting the number of outcomes in which four 6-sided dice don't all show the same number would require some pretty delicate casework.

However, counting all the outcomes in which four 6-sided dice do all show the same number is very easy:

there are only 6 ways this can happen, namely all ones, all twos, all threes, all fours, all fives, and all sixes.

So since there are $6^4$ total outcomes, we can conclude that

$$ P(\text{4 dice all show the same number}) = \frac{6}{6^4} = \frac{1}{6^3} = \frac{1}{216}. $$

Therefore, using the principle of complementary probabilities, we can conclude that $$ P(\text{4 dice don't all show the same number}) = 1 - \frac{1}{216} = \boxed{\frac{215}{216}}. $$

Sorry if this didn't come out right, but the answer would be 215/216 :) Hope this helped.

I was looking back, and you did repost. We all got different answers. 

Hey Mellie, what was the address of the post that we all got different answers on?

I'm sorry: 

http://web2.0calc.com/questions/what-is-the-probability-that-when-we-roll-four-fair-6-sided-dice-they-won-t-all-show-the-same-number

It was very recent. CPhill's answer.

Yes I get the same as Mellie - I put my answer on the original question :)

Hi Mellie

Oh yes I saw CPhill answer it too but that was AFTER I made my comment.

I must have got it confused with a similar question. 

Sorry anon :)

CPhill did it the same as us - he just made a little error when he simplified his fraction :)