Solve this puzzle

There are 100 doors in a row numbered from 1 to 100. Initially all
are closed. Then you make 100 passes by the 100 doors. In pass 1 you
toggle the all the doors (1,2,3,4…)starting from the first door.
In the second pass you toggle every second door(2,4,6,8,…). In the
third pass you toggle all third doors (3,6,9…). Similarly you make
100 passes.

what state are the doors in after the last pass?

which are open which are closed??

perfect square number will be opened because perfect square will have odd number of divisors.

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