Question

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) 1/12 b)0 c)12/212 d)11/12

Answer 1

Zero.

If one letter is in wrong envelope, one other letter must also be in wrong envelope. So zero is the probability that exactly 1 letter is inserted in an improper envelope