Question 1108677
An elevator with two passengers stops at the second, third, and 
fourth floors. If it is equally likely that a passenger gets off 
at any of the three floors, what is the probability that the 
passengers get off at different floors?<pre>First we get the numerator of the probability:

There are 3 ways to pick the floor for passenger 1 to get off.
For each of those 3 ways to pick the floor for passenger 1 to get 
off, there remain 2 ways to pick a different floor for passenger 2 
to get off.

So the numerator of the probability is 3×2 or 6.

Next we get the denominator of the probability:

There are 3 ways to pick the floor for passenger 1 to get off.
For each of those 3 ways to pick the floor for passenger 1 to 
get off, there are still 3 ways to pick a floor for passenger 
2 to get off.

So the denominator of the probability is 3×3 or 9.

Answer: {{{matrix(1,5,6/9,which,reduces,to,2/3)}}}

Edwin</pre>