find the number of ways in which 5 letters can be put in the 6 envelopes such that no letter goes into the correct envelope . how the answer will be changed if number of envelopes is changed to 5.
For the second part answer is : 44
Using Principle of Inclusion and Exclusion we can solve this problem
n=6! - 5*5! + 10*4! -10*3! + 5* 2! -0 = 720-600+240-60+10=310
Hope it is correct
hi varun
what is the principle of exclusion and inclusion. could you please explain me in detail how you solved it
the question is of derangement .
the formula to derange r objects is:
r![1 - 1/1! + 1/2! - 1/3! +1/4! -----------1/r!]
the formula to derange r objects out of n is:
nCr * r! [1 - 1/1! + 1/2! - 1/3! + 1/4!--------------1/r!]
hope your questions are answered now.
ruchika
the answer for first is 720-120-24-6-2=568
the answer for second is 120-24-6-2=88
if this solves your problem send me by writing correct as a reply