How many ways can 5 books be arranged on a shelf?

Explanation

• Arranging 5 different books in a row is 5! = 5 × 4 × 3 × 2 × 1 = 120.
• Think of the slots: the first has 5 choices, the next 4, then 3, then 2, then 1, and multiplying gives 120.
• Order matters on a shelf, so this is a permutation rather than a combination.
• Option A 24 is 4!, which would be the answer for only 4 books.
• If two books had to stay together, treat them as one unit and the count drops to 4! × 2 = 48.