In how many ways can 12 books be arranged on a shelf if:
(a) 4 particular books must always be together.
(b) 2 particular books must occupy the first position and the last position.
Answers
Answer:
ans (a)= two ways
ans b = one way
Total number of Ways = 9! * 4! if 4 particular books must always be together. & 10! * 2 ways if 2 particular books must occupy the first position and the last position.
Step-by-step explanation:
Total Books = 12
(a) 4 particular books must always be together.
Take 4 books as 1 & remaining books = 8
Total Books = 9
9 books can be arranged in 9 ! ways
4 books as 1 can be arranged in 4! ways
Total number of Ways = 9! * 4!
(b) 2 particular books must occupy the first position and the last position.
2 Books can be arranged in 2! = 2 ways
Remaining 10 books can be arranged in 10! Ways
Total number of Ways = 10! * 2
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