An algebra problem by Mayank Rai

Algebra Level 2

Five different books (A, B, C, D and E) are to be arranged on a shelf. Books C and D are to be arranged first and second starting from the right of the shelf. The number of different orders in which books A, B and E may be arranged is

3!*2! 2! 5! 3!

Mayank Rai by Mayank Rai , 25, India

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1 solution

Sravanth C.
May 7, 2015

Here we have 3 books which are to be arranged, as the books C and D have already been given fixed posistions.

Therefore the possible permutation is P n , r = P 3 , 3 = n ! ( n − r ) ! = 3 ! ( 3 − 3 ) ! P_{n,r}=P_{3,3}=\dfrac{n!}{(n-r)!}=\dfrac{3!}{(3-3)!}

= 3 ! 0 ! = 6 1 = 6 =\dfrac{3!}{0!}=\dfrac{6}{1}=6

3 Helpful 0 Interesting 0 Brilliant 0 Confused

So how is 6 the answer 3?

Sannah Evangelista - 4 years, 5 months ago

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