Question

there are lockerslined up numbered 1 to 1000.They are all closed . i walk by and open all the lockers . then Al walks by and goes to every second locker starting at #2and closes it. Then Mary goes to every third locker starting with #3 closing the opeaned lockers and opening the closed lockers. The n Jose walks by and goes to every fourth locker starting at #4 closing the opened locker and openining the closed lockers. this rutine goes on untile eviline goes to locker 1000 and closes it . After this is over which lock ers will be open?why?

I don't remember the answer and I'm not necessarily going to sit down and figure this out. BUT....I will give you a hint I THINK is a correct hint:

Think about prime numbers.

I apologize if it's not. But my dad gave me this question (or a similar one) years ago and I think I remember that being part of the answer.

Matt