Directions
Read the following questions. Choose the right answer.
There is only ONE correct answer to each question.
The number of possible arrangements of five different books on a shelf, such that two particular books are always next to each other, is:
- 4!
- 2×4!
- 5!
- 2×5!
Show answer
Correct answer: B. 2×4!
Why
Treat the two particular books as one combined unit, giving 4 units to arrange (4! ways), and the two books within that unit can be ordered 2 ways — total 2×4!.