I bought a brand new car and decided to visit my friend on the very next day. It took me an hour and a half to reach his place. I decided to call it a day and return back to my house at night. I was surprised that I was able to reach back home in just 90 minutes despite the fact that I drove at the same speed.
This is a classic chess puzzle and considered to be one of the hardest puzzles in history.
As shown in the picture below, White army is arranged in a classic chess board. You need to add black army i.e
in such a way that not a single piece of either color is under attack.
A petri dish kept in a lab has a colony of healthy bacteria. Every bacterium divides itself into two in exactly two minutes. Now the colony started with a single cell at 2 pm. If the petri dish was exactly half full of bacteria at 3 pm, when will the dish become full of bacteria?
Since every bacterium divides into two in two minutes and we know the fact that the dish was half filled with bacteria at 3 pm, after exactly 2 minutes, all will divide into two and will fill the petri dish. Thus, the petri dish will become full at 3:02 pm.
Alan is an honest person who never speaks a lie. He thinks of a number among 1, 2 and 3. Now, you can ask him only one question and that too for which the answer that you will receive will be in the form of yes, no or don't know. But he will reply only truth fully.
What will you ask from his so that you can know the number he is thinking of?
The store room of your house is locked with a certain lock that can be closed without a key but requires a key to open which you own (there is no duplicate key). You decide to move your old stuff in the storeroom. After keeping the things carefully, you lock it back again perfectly. The next day, a dead body is found in your closed store room. Since only you have the key to the store room and you live alone, the police suspects you as a murderer. You can’t understand anything when suddenly a thought strikes your mind. There is a possible way using which the dead body could have been placed by someone else.
Can you find that way so you can tell the police and prove yourself to be innocent?
When you were inside the shed, the murderer replaced the lock with his own one that was identical to your original lock. When you locked the store room, you did not require a key and there was nothing abnormal for you. When you left, the murderer opened the lock with his key, planted the dead body inside and replaced the lock again putting the original lock in the place. He then closed it without any problem.
As shown in picture, there are four gears with the following specification
* Gear A has 60 teeth
* Gear B has 40 teeth
* Gear C has 20 teeth
* Gear D has 60 teeth
* Every minute, Gear B makes 15 complete turns.