100 Doors Puzzle || Hard Puzzle for Genius minds

LOGICALLY YOURS
LOGICALLY YOURS
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Published 2018-05-13
There are 100 doors in a row. They all are initially closed.
A person walks through all the doors 100 times and every time he toggles the state of speific doors. that means he changes
the state of the door,. if the door is closed, he will open it.. and if its opened then he will close it.
In each walk he selects specific doors to toggle, in the following manner.

In his first walk, he toggles all the doors in multiple of 1.. that means he toggles all the 100 doors.
In the second walk, he toggles the doors in multiple of 2.
In the third walk, he toggles the doors in multiple of 3. that means, he will change the state of door no.3, 6, 9, 12... and
so on.
In the fourth walk he toggles doors in multiple of 4.

This way he walks for 100 times.

The puzzle is : What door numbers will remain opened after 100 walks.
(Remeber that initially all doors are in closed state)

This video explains this puzzle the best way. You will certainly learn the optimal way and the best approach of solving difficult puzzles.

Also try these mind blowing puzzles:
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All Comments (21)
  • @lokeshreddy212
    Very difficult puzzle, but your explanation is very detailed. Thanks a lot for making this video....
  • @kiranvootori8101
    I can imagine how difficult making the animation would have been and appreciate how it makes understand the problem and approach to the solution so easy. But, I loved the door opening progress bar more than anything else - very creative.
  • @kanishkkrishna9983
    Really amazing explanation.Actually I was asked to solve this using programming.I even solved it in C++ by factor of a no. You are a genius sir. I never thought about square logic.
  • @jaygreen7494
    I love this type of puzzle, because you feel clever if you figure it out, but if you have to see the explanation it seems so simple and you wish you'd thought of it.
  • @bhaveshkhanted7087
    After completing the puzzle by writting all the factors till 100. Me : i am the most clever in the world. After video explanation.. Me : Oh , just missed that.
  • @TigruArdavi
    Im too lazy, that's why I so love spreadsheets. Quickly drew up an excel, and instantaneously realized it's only square numbers remaining. That's the solution, so I didn't inquire it any further, appreciate your approach and explanation.
  • @girlnado
    Kinda proud of myself on this one. I usually suck at these problems but I was able to work through it on my own, find the patterns, and get the right result. Very fun!
  • @shauryaagarwal4556
    This came in my Olympiad yesterday and today this is in my recommendation!!!! Aliens Confirmed
  • @navdeepsingh6204
    Incredible approach..... Totally out of the box ..... Great to watch such a solution....keep it up
  • @d4django
    Very interesting. Excellent explanation. And an interesting fact about squares.
  • @MrRobertpaul80
    Loved the explanation. Very very well done video! Thank you!