# Calculating n given r and nCr?

moonman239
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.

mjpam
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 $_{n}C_{r}$?

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