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Question

Mathematics Question on permutations and combinations

If the four letter words (need not be meaningful ) are to be formed using the letters from the word "MEDITERRANEAN""MEDITERRANEAN" such that the first letter is RR and the fourth letter is EE, then the total number of all such words is :

A

11!(2!)3\frac{11!}{(2!)^3}

B

110110

C

5656

D

5959

Answer

5959

Explanation

Solution

M, EEE, D. I, T, RR, AA, NN
RE\frac{R}{ }--\frac{E}{ }
Two empty places can be filled with identical letters [EE, AA, NN] \Rightarrow 3 ways
Two empty places, can be filled with distinct letters [M, E, D, I, T, R, A, N] 8P2\Rightarrow ^{8}P_{2}
\therefore Number of words 3+56=59

or

3+8P2=593+^{8}P_{2}=59