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Question
If tr denotes the number of 1−1 function from {x1,x2...xr} to {y1,y2,..yr} such that f(xi)≠yi∀i=(1,2,3..r) then t4 equals
If tr denotes the number of 1−1 function from {x1,x2...xr} to {y1,y2,..yr} such that f(xi)≠yi∀i=(1,2,3..r) then t4 equals
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Solution
The correct option is B 9
This is equivalent to having r letters and corresponding r envelopes. The letters are placed such that no letter goes into the corresponding envelope i.e. all letters are placed wrongly.
Here, there are 4 letters and 4 envelopes.
Thus, the number of ways = 4!(12!−13!+14!)=9
Hence, (C) is correct.
This is equivalent to having r letters and corresponding r envelopes. The letters are placed such that no letter goes into the corresponding envelope i.e. all letters are placed wrongly.
Here, there are 4 letters and 4 envelopes.
Thus, the number of ways = 4!(12!−13!+14!)=9
Hence, (C) is correct.
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