Question

Your five favourite puzzle books are displayed between two book ends in your study. If you decide to arrange the five books in every possible combination and move just one book every minute, how long would it take you? Select one: a. 5 hours b. 3 hours c. 4 hours d. 2 hours

Answer 1

a. 5 hours............

Answer 2

Answer:  

Total time needed to move the books = 4 hours

Step-by-step explanation:

Total number of favorite puzzle books = 5

So, Total number of arrangements to arrange 5 puzzle books = 5!

⇒ Possible arrangements = 5 × 4 × 3 × 2 × 1

                                            = 120

Now, One book is moved in 1 minute

So, Time taken to move books in 120 ways = 120 minutes

For making a new arrangement , two books are required to be moved.

Therefore, Total time needed to move the books = 2 × 120

                                                                                     = 240 minutes

                                                                                     = 4 hours