Suppose you and your 4 friends (5 people) are dressing up as the 6 main characters of the first Avengers movie: Iron Man, Hulk,
Thor, Black Widow, Captain America and Hawkeye. (each question is independent of the others.) How many ways can you do this if all 5 people dress up as a different character?
If every person has to choose a different character, the first person to choose a character has 6 options, the second has 5, the third has 4, the fourth has 3, and the last person has only two options. Therefore, the total number of ways you can do this if all 5 people dress up as a different character is:
