100 doors in a row problem

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??

Unusual paragraph

What is unusual about this paragraph? You will find that this is not
just an ordinary paragraph if you look at its words. An odd group of
words this is! Can you find what it is?

Golo is locked in a cave !!!

Golo is locked in a cave. He is having 2 vessels with him (5ltr & 7ltr).
The gate of the cave will open only when there are exactly 6 litres on
the handle. He can take as much water as he want from the nearby
water well. How he can make combinations such that the 7 ltr vessel
will have exactly 6 liters of water?

64 = 65 Geometry Paradox

Comparison of the areas of the 2 shapes creates a paradox: 64 = 65

How is this possible?