Question
In how many ways can you put 7 letters into their respective envelopes such that exactly 3 go into the right envelope?___.
Answer:
:
No of ways in which the 3 correct envelopes can be selected= 7C3=35
Derangement of 4 envelopes & letters = 9 (derangement value for 4 is 9)
Total No of ways of arrangement = 9×35 = 315
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:
No of ways in which the 3 correct envelopes can be selected= 7C3=35
Derangement of 4 envelopes & letters = 9 (derangement value for 4 is 9)
Total No of ways of arrangement = 9×35 = 315
Was this answer helpful ?
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