Assignment:
A school had a very unusual tradition involving its 1000 students and its 1000 lockers. On opening day, after the head of the school had closed all the lockers, a student walked by and opened every single one. A second student then closed every second one (#2, 4, 6, 8 etc). A third student then changed every third locker (#3,6,9,12 etc), that is, she opened the ones that were closed and closed the ones that were open. A fourth student then changed every fourth locker, after which a fifth student changed every fifth locker , and so on until all 1000 students had passed by all 1000 lockers. At the end of this strange activity, which lockers were open?
Provide complete and step by step solution for the question and show calculations and use formulas.