Stupid mailman
A mailman is asked to deliver four letters to four houses, and each letter is assigned to a different house. However, the mailman mixed up the addresses so he doesn't know which letter belongs to which house. Therefore, at each house, he gives a random letter.
What is the probability that the mailman gave the correct letter to exactly three houses?
Give your answer to 2 decimal places.
The answer is 0.00.
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1 solution
If the mailman gave the correct letter to three houses, the fourth house also has the correct letter. (Contradiction!)
Therefore it is impossible for the mailman to give the correct letter to exactly 3 houses and the probability is 0.