Question

1000 students 1000 boxes. 1st student opens all boxes. 2nd student closes all 2nd, 4th, 6th ..... So on. 3rd student closes 3rd, 6th, 9th boxes (if any of then already opend), and opens (if any of then already closed)..... This process continues till 1000 th student. Then how many boxes will be opened at the end.

Answer 1

Answer:

I think 5 boxes are opened