Calculating n given r and nCr?

Main Question or Discussion Point

I wish to calculate the number of objects in the population I'm selecting from, given that I am choosing r objects and there are nCr different combinations.

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I wish to calculate the number of objects in the population I'm selecting from, given that I am choosing r objects and there are nCr different combinations.
Do you know the equation for $_{n}C_{r}$?

chwala
Gold Member
kindly read on combinations and permutations and be specific..

HallsofIvy