There are 40 students in our class How many ways they can be

There are 40 students in our class. How many ways they can be lined up such that two fixed students X and Y are next to each other (order of the two fixed students does not matter).

Solution

So now that X and Y are always beside each other, then you can treat them as just ONE PERSON.

Thus, it\'s like there are now just 39 people to permute.

As n! = number of ways to permute n objects in a line, then the number of ways is

#ways = 39! = 2.03979*10^46 [ANSWER]