Well Waddaya Know XX

Last week's Q & A:

I have 10 marbles - 5 red, 2 green, and 3 blue. How many different ways can I line them up?

2,520	10 (37%)
3,628,800	9 (33%)
120,960	5 (18%)
4,032	3 (11%)

Votes so far: 27

Ezzie: For what it's worth, while I knew what had to be done, I could not remember how to figure it out; I still realized it had to be 2,520 (the other numbers were too high), but it was very tricky.

Shragi:

10!
_____ =
5!*3!*2! 2520

10! = arrangement of 10 marbles
since switching around 2 (for example) red marbles gives the same
arrangement twice we remove all the possibilities which repeat
themselves.
Therefore we divide by 5! (=possibilities to arrange the reds)
3! (= possibilities to arrange the blues)
2! (= possibilities to arrange the greens)

This week's question is up to the left.