This very much depends on the specification of the computers in question, and so more information would be required in order to answer this question accurately. It would be worthwhile contacting an IT expert for advice specific to your own needs.
There are many computers in a server rack. Generally there are between 15 and 100 computers on a server rack depending on the size of the business and or building.
World of Warcraft can be installed on as many computers as you want. The problem is that you need a CD key and a account to play but you can use the same account on every computer you have it installed it on. I.e. you can have any number of computers but you have to pay for a serial number to create your account - each account is separate and costs $15/month to have.
5 through 6 computers average in 1 regular classroom and if in gifted or magnet 10 through 15 average in 1 classroom.
about 15 million
15
You need 225 tiles. :)
Home/Small office level router can handle about 10-15 computers, if you have more than that you will experience problems with connection as well as connectivity.
15.
15
The answer depends on the size of each brick.
15 feet is the same as 4,572 millimeters.
The amount of copies is irrelevant; choose as many as you need.