Question

How many ways to put 4 different rings in 5 fingers?

Answer 1

First ring can be worn in 4 ways (on any of the four fingers);
Second ring can be worn in 5 ways (as it can go on any of four fingers - 4 ways; plus it can go below the first one - 1);
Third ring can be worn in 6 ways (the same logic as for the second ring);
Fourth ring can be worn in 7 ways;
Fifth ring can be worn in 8 ways;

Total: 4*5*6*7*8=6720