After the typist writes 12 letters and addresses 12 envelopes, she inserts the letters randomly into the envelopes (1 letter per envelope). What is the probability that exactly 1 letter is inserted in an improper envelope?
a)0
b)12/212
c)11/12
d)1/12

• obviously 0
  because, if exactly one letter is inserted to improper envelope that means all the remaining letter are inserted to right once
  if all the remaining letter are inserted to the right once that means now the one letter remaining is also inserted to right one
  so that is impossible event
  so the answer is 0
  
• 8 years agoHelpfull: Yes(0) No(0)
• 12 letters are addressed to 12 people.
  If 1 of those letter is inserted improperly then ..
  1 more letter which replaces the 1st will be posted to wrong address
  Therefore, the probability of inserting exactly 1 letter incorrectly is 0. (atleast 2 letters will get improper envelope)
• 8 years agoHelpfull: Yes(0) No(0)