The rules of a secret santa are that each person’s name is put in a hat and the names are mixed. Then each person must choose 1 name from the hat. If you choose your own name, you must put it back in the hat.
If 2 people do a secret santa there is only one solution: Person A gives to person B and person B gives to person A.
Stage 1: With 3 people, there are 2 possible ways. Can you think why?
Stage 2: Now how many different ways are there with 4 people?
The final challenge is to find the number of different scenarios with 5 people.
Solutions can be found here.