In how many ways can 10 examination papers be arranged so that the best and the worst papers never come together?

Question: In how many ways can 10 examination papers be arranged so that the best and the worst papers never come together?

Solution:
No. of ways in which 10 paper can arranged is 10! Ways.
When the best and the worst papers come together, regarding the two as one paper, we have only 9 papers.
These 9 papers can be arranged in 9! Ways.
And two papers can be arranged themselves in 2! Ways.
No. of arrangement when best and worst paper do not come together,
= 10! - 9! × 2!
= 9!(10 - 2)
= 8 × 9!