Three letters are dictated to three person and an envelope is addressed to each of them, the letters are inserted into the envelopes at random so that each envelope contains exactly one letter. Find the probability that at least one letter is in its proper envelope.

Explanation

To solve the problem of finding the probability that at least one letter is in its proper envelope when three letters are randomly placed into three envelopes, we can follow these steps:

### Step 1: Determine the Total Arrangements
First, we need to calculate the total number of ways to arrange the three letters in the envelopes. Since there are 3 letters, the total arrangements can be calculated using the factorial of the number of letters:

\[ \text{Total arrangements} = 3! = 6 \]
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