Hello, csy0961743!

7 passengers enter an elevator on the first floor of an 11-floor building.

Assume that the egress pattern to floors 2,3, ... ,11 is the same.

What is the probability that all get off at different floors?

Each of the 7 people have 10 choices of floors on which to exit.

. . There are: . possible outcomes.

How many ways can they exit onfloors?different

There are: . ways.

Answer: .