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The 11 players can be arranged in 11! ways.

Hence, except for the two players who are in incorrect positions all other players are in correct positions.

Number of ways to select two players = 11C2 = 55

Number of ways to arrange the players = 1

Required probability = 55/11!


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Answer: D

11 players can be arranged in 11! ways.
We need to find the number of cases in which, by switching exactly two players with each other, the players will be standing in alphabetical order of their names.
This is equivalent to finding the number cases in which only two players are not standing in alphabetical order of their names.
A B C D E F G H I J K

Player 'A' can be switched by 10 other players.
Similarly, player 'B' can be switched by 10 other players. But since we already counted 'A' to replace 'B' above, we have 9 other options.
player 'C' will have 8 other options available.
player 'D' will have 7 other options available.
.
.
Lastly, player 'J' will have 1 other unconsidered option left i.e., to swap with player K.

Sum of all possible cases = 10+9+8+7..+1 = 10*11/2 = 55

Hence, probability that by switching exactly two players with each other, the players will be standing in alphabetical order of their names = \(\frac{55}{11!}\)
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The 11 players can be arranged in 11! ways.

Hence, except for the two players who are in incorrect positions all other players are in correct positions.

Number of ways to select two players = 11C2 = 55

Number of ways to arrange the players = 1

Required probability = 55/11!


IMO D
­gmatophobia

Just wanted to confirm my understanding is corrrect. Why it is 55/11! and NOT 110/11!

Is it because let's say we have
xx..xxab
xx..xxba
Both will be present in total 11!
But, only 1 way is correct way(alphabetical order) ab and NOT ba?
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Bunuel
11 players of the Portugal National Football Team are standing in a row in random order. If no two players of the Portugal National Football Team have the same name, what is the probability that by switching exactly two players with each other, the players will be standing in alphabetical order of their names ?

A. \(\frac{1}{11!}\)

B. \(\frac{2}{11!}\)

C. \(\frac{5}{11!}\)

D. \(\frac{55}{11!}\)

E. \(\frac{110}{11!}\)



 


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­
probability is just (no. of favourable states)/(total number of states)

so here, total number of states in which these 11 guys can be arranged is 11!

Now, to find the favourable states, a favourable state is any arrangement in which exactly 2 guys are in wrong position, that is, they are swapped

So, assume they all are standing in alphabetic order, so the number of ways to swap any 2 guys is 11C2 = 55

hence probability = 55/11!
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