Question

In how many ways five different rings can be put on four fingers with at least one ring on each finger?
A. 120
B. 480
C. 240
D. 960

Answer 1

Since at least one ring is to be put in each finger. So, we select four rings out of 5 and then they are arranged in fingers. This can be done in `""^(5)C_(4)xx4!` ways. Now, either above the ring already placed on it or below it.
So, the required number of ways `=""^(5)C_(4)xx4!xx4xx2=960`