1. The formula for combinations is: nCr = n! / (r! * (n – r)!), where n is the total number of items, r is the number of items we want to choose.
2. C(n,r) = the number of permutations /number of ways to arrange r objects. [Since by the fundamental counting principle, we know that the number of ways to arrange r objects in r ways = r!] C(n,r) = P (n, r)/ r! C(n,r) = n!
3. There is a way you can calculate permutations using a formula. This formula is: P(n,r) = n! ÷ (n-r)!
