GATE CSE
First time here? Checkout the FAQ!
x
+1 vote
17 views
Vijay wrote  4 different letter to send to 4 different addresses .for each letter, he prepared one envelope with its correct address. if the four letters are to be put into 4 envelopes at random in how many ways can we put the letters so that only two of the letter goes to the right envelope?

2

4

1

6
asked in Combinatory by Active (1.8k points)   | 17 views

1 Answer

+1 vote
Best answer

For this, first we select two letters whose position is correct.. This can be done in 4C2 ways = 6 ways.. 

For the remaining two letters,  we need to do derangement which is done in D= 2!/2 = 1 way.. (the only way to derange two objects is to swap them).. 

Hence number of ways = 6 * 1 = 6.. Hence D)  should be correct option.. 

answered by Veteran (77.1k points)  
selected by
Thankyou....


Top Users Sep 2017
  1. Habibkhan

    7166 Points

  2. Warrior

    2640 Points

  3. Arjun

    2574 Points

  4. rishu_darkshadow

    2520 Points

  5. A_i_$_h

    2280 Points

  6. nikunj

    1980 Points

  7. manu00x

    1846 Points

  8. makhdoom ghaya

    1770 Points

  9. Bikram

    1744 Points

  10. SiddharthMahapatra

    1718 Points


26,144 questions
33,726 answers
79,957 comments
31,116 users