I have 5 books, two of which are identical copies of the same math book (and all of the rest of the books are different).  In how many ways can I arrange them on a shelf?
Question:
I have 5 books, two of which are identical copies of the same math book (and all of the rest of the books are different).  In how many ways can I arrange them on a shelf?
Answer:
Let's think step by step.

user
60
I have 5 books, two of which are identical copies of the same math book (and all of the rest of the books are different).  In how many ways can I arrange them on a shelf?
train