Melody

That is excellent Krxzy    

Thank you Bginner for your correct answer.

Guest you sound like a smart #@#  and that will not get you far in life.

Using Catmg's combinations that do not appear to be in question

1, 1, 4, 6       

1, 2, 2, 6

1, 2, 3, 4

2, 2, 2, 3

Assume all the dice are different in colour.  (That will make it much easier)

Also assume that the dice are rolled one at a time.  It is probably easier to act as if order counts.

That means they are all unique and a green 1 is different from a blue 1

The total number of combinations is 6^4=1296,   just as catmg found.

Each of those 4 combinations above can be formed in 4! ways.  But I do need to allow for the double counting here

1, 1, 4, 6       4!/2 = 12

1, 2, 2, 6        4!/2 =12

1, 2, 3, 4           4!=24

2, 2, 2, 3           4

total  52

So we have a prob of    52/1296 =  13/324

I am not 100% sure that this is correct .......      But it is the same as guest found so maybe it is ok.

It is a nice example of LaTex formating too.

Yes, I got that.  thanks :)

The better question would be......

Given.

Question: Dr. Worm leaves his house at exactly 7:20 a.m. every morning.
When he averages 30 miles per hour, he arrives at his workplace ten minutes late.  
When he averages 40 miles per hour, he arrives at his workplace five minutes late.  
When he averages 60 miles per hour, he arrives fifteen minutes early.

Given the simplest version of this data. (no breakfast breaks, no breakdowns etc) 

Prove that this set of data cannot be valid.

Thanks guest but next time please answer on the original post and just leave a little note here saying that you have done so.

Another link

EP has answered it.  Thanks EP.

ok.

Thanks for letting me know.