### Instruction: Determine the number of ways to arrange the letters of the word RADII.### Response: I know that if I had five distinct letters, I could arrange them in 5! = 120 ways.
But since the letter I appears twice, I have to account for the fact that swapping the two I's does not create a new arrangement.
So I have to divide by the number of ways to arrange the two I's, which is 2! = 2.