There was such a thread earlier. It's a wonder no one has started one yet.
Let me start with a simple puzzle:
What are the total number of different scores that you can get on a single Nerdity test?

Possible scores for question: 0, 3, -1
15 questions
so 0, 1, 2, 3, ... 39, 41, 42, 45

Proof: We can look at it this way: 45 - (linear combination of -4 and -3).
Largest number you can't get by adding 3s/4s is 5. So under 40 works.
40: you need 3*14+2*-1 (16>15)
43: you need 45-2 (17>15)
44: you need 45-1 (16>15)

Puzzle thread = dead.

A math puzzle!

There are 5 floors in a school. There are 20 classrooms on each floor, and there are 30 students in each classroom. There's enough lockers in the whole school to accomodate everybody, and each floor has an equal amount of lockers. On the floors, there are an equal amount of people from each floor that have a locker there (E.x. 500 lockers means 100 people from Fl. 1, 100 people from Fl. 2, etc.)
You can leave the school from any floor.

1) At the end of the school day, assuming that all students directly go to their lockers and out, which section of stairs is the busiest?

2) Even more complicated. There are the same number of classrooms and students attending the classes on each floor. Say the number of lockers on each floor (F1, F2, F3, F4, F5) have a ratio of 1:2:3:4:5, respectively. The number of students from each floor that have a locker on that floor have a ratio of 5:4:3:2:1, also respectively. Which section of stairs is the busiest now?

No, it's not my homework. My homework is graphing linear inequalities. This was a problem I made during the lunch break at a math contest, and later elaborated on.

Hope it was hard :|

The exams were that bad?

[5F]
840 students
[4F]
1200 students
[3F]
1200 students
[2F]
840 students
[1F]F
therefore, the busiest staircases are between 2F and 3F and 3F and 4F
you can exit from any floor, right?