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?
Choose the most appropriate option: A) 1/2 B) 6/7 C) 0 D) 1/12 E) 1/55
Explanation :   Answer is Zero. Question is asking whether there is any chances of one letter getting inserted in an improper envelope, but there can-not be onr case as if one gets improper there is another letter who will be inserted in the improper envelope too...   Hence C is the answer.   Answer : 0
<result>C</result>
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?