求解一道PREP数学，后天就要考了~急

audrey1007

Tanya prepared 4 different letters to be sent to 4 different addresses. For each letter, she prepared an envelop with its correct address. If the 4 letters are to be put into the 4 envelops at random, what is the probability that only 1 letter will be put into the envelop with its correct address? 答案是三分之一

zhanghan666

1/4*2/3*1/2*4