I would think this is a combination question because order does not matter. As long as 2 books are picked, it doesnt matter which book is picked. Is the answer given by the book wrong or someone please explain why?
How many different ways can 4 books be arranged 2 at a time?
The order of arrangement matters in this problem. Therefore, this is a permutation problem. The number of permutations of n objects taken r at a time is:
P(n,r) = n!/(n-r)!
P(4,2) = 4!/(2!)
P(4,2) = 24/2
P(4,2) = 12
How many ways you can select 2 from 4C2 = 6
Each of this selection can be arrange in 2! ways = 2
Answer is 6*2 = 12
So it is a combintion and permutation problem.
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