permutation, probabilities, possibilities

[You]

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I suck at the "p-p-p" 🙂 I keep on getting this 1/2 right and the ones I missed because my assumption of "order is not important" was wrong. Anyone has a good link on demystifying this crap?

 

[fancymylotus]

I suck at the "p-p-p" 🙂 I keep on getting this 1/2 right and the ones I missed because my assumption of "order is not important" was wrong. Anyone has a good link on demystifying this crap?

i think when order matters, its P: n!/r-n! and when it doesnt matter, its C: n!/r!-(r-n)!

 

[You]

How did Dr. R came up with the long formula for Math #64? Or is that just standard and just gotta memorize...