5 people go to a movie theathre. They consign their hats to a cloakroom. What is the probability that when they leaved the theathre 2 of them got their hats?
Five people go to a movie theatre and consign their hats to a cloakroom.
What is the probability that when they leave the theatre, exactly 2 of them got their hats?
Assuming that the hats are returned randomly,
. . there are possible outcomes.
Call the people
First, choose the two people who get their hats.
. . There are: . choices.
Suppose they are and
Then do not get their hats.
There are 2 choices: . and
Hence, there are: . ways.
The probability is: .