Question

In how many ways can $3$ identical rings be worn on $4$ fingers if any number of rings can be worn on any finger?

Answer 1

Rings are identical

Here $n=3,p=4$

Using the formula from Beggar’s method,
${}^{n+p-1}{C}_{p-1}={}^{3+4-1}C4-1={}^6{C}_3=20$