Question

Between two ends of a bookshelf in your study are displayed five of your favourite puzzle books. If you decide to arrange these five books in every possible combination and move just one book every minute, how long would it take you to do so?

• A. One hour
• B. Two hours
• C. Three hours
• D. Four hours

Answer 1

The correct option is B Two hours

Number of ways of arranging 5 books
=$5!=5\times 4\times 3\times 2\times 1=120$
$\therefore Totaltime=120\times 1minutes=2hours.$