Prisoner and lightbulb
Posted on May 11, 2014
(Last modified on August 7, 2020)
| 2 minutes
| Kinshuk Chandra
Problem There is a prison with 100 prisoners, each in separate cells, which are sealed off, soundproof and windowless. There is a lobby in the prison with a lightbulb in it. Each day, the warden will pick one of the prisoners at random (even if they have been picked before) and take them out to the lobby. The prisoner will have the choice to flip the lightbulb switch if they want.
[Read More]Travelling MONK
Posted on May 11, 2014
(Last modified on August 7, 2020)
| 1 minutes
| Kinshuk Chandra
A monk leaves at sunrise and walks on a path from the front door of his monastery to the top of a nearby mountain. He arrives at the mountain summit exactly at sundown. The next day, he rises again at sunrise and descends down to his monastery, following the same path that he took up the mountain.
Assuming sunrise and sunset occured at the same time on each of the two days, prove that the monk must have been at some spot on the path at the same exact time on both days.
[Read More]Leap year Birthday
Posted on May 11, 2014
(Last modified on August 7, 2020)
| 1 minutes
| Kinshuk Chandra
Problem Bill and Stacie are delighted when their new baby, Patrick, is born on February 29th, 2008. They think it’s good luck to for him to be born on the special day of the leap year. But then they start thinking about when to celebrate his next birthday. After some thought, they decide that they want to celebrate Patrick’s next birthday (when he turns 1) exactly 365 days after he was born, just like most people do.
[Read More]Crossing the BRIDGE past the GUARD
Posted on May 11, 2014
(Last modified on August 7, 2020)
| 2 minutes
| Kinshuk Chandra
Problem A guard is stationed at the entrance to a bridge. He is tasked to shoot anyone who tries to cross to the other side of the bridge, and to turn away anyone who comes in from the opposite side of the bridge. You are on his side of the bridge and want to escape to the other side.
Because the bridge is old and rickety, anyone who tries to cross it does so at a constant speed, and it always takes exactly 10 minutes to cross.
[Read More]NEWYORK HAIR (Pigeonhole Principle)
Posted on May 11, 2014
(Last modified on August 7, 2020)
| 2 minutes
| Kinshuk Chandra
Problem You are visiting NYC when a man approaches you.
“Not counting bald people, I bet a hundred bucks that there are two people living in New York City with the same number of hairs on their heads,” he tells you.
“I’ll take that bet!” you say. You talk to the man for a minute, after which you realize you have lost the bet. What did the man say to prove his case?
[Read More]Paying with RINGS
Posted on May 11, 2014
(Last modified on August 7, 2020)
| 2 minutes
| Kinshuk Chandra
Problem A man comes to a small hotel where he wishes to stay for 7 nights. He reaches into his pockets and realizes that he has no money, and the only item he has to offer is a gold chain, which consists of 7 rings connected in a row (not in a loop).
The hotel proprietor tells the man that it will cost 1 ring per night, which will add up to all 7 rings for the 7 nights.
[Read More]The MISSING Servent
Posted on May 11, 2014
(Last modified on August 7, 2020)
| 2 minutes
| Kinshuk Chandra
Problem A king has 100 identical servants, each with a different rank between 1 and 100. At the end of each day, each servant comes into the king’s quarters, one-by-one, in a random order, and announces his rank to let the king know that he is done working for the day. For example, servant 14 comes in and says “Servant 14, reporting in.”
One day, the king’s aide comes in and tells the king that one of the servants is missing, though he isn’t sure which one.
[Read More]TRUTH OR LIES
Posted on May 11, 2014
(Last modified on August 7, 2020)
| 2 minutes
| Kinshuk Chandra
Problem You’re walking down a path and come to two doors. One of the doors leads to a life of prosperity and happiness, and the other door leads to a life of misery and sorrow. You don’t know which door is which.
In front of the door is ONE man. You know that this man either always lies, or always tells the truth, but you don’t know which. The man knows which door is which.
[Read More]Engineers & Managers
Posted on May 11, 2014
(Last modified on August 7, 2020)
| 5 minutes
| Kinshuk Chandra
Problem You have just purchased a small company called Company X. Company X has N employees, and everyone is either an engineer or a manager. You know for sure that there are more engineers than managers at the company.
Everyone at Company X knows everyone else’s position, and you are able to ask any employee about the position of any other employee. For example, you could approach employee A and ask “Is employee B an engineer or a manager?
[Read More]Worm Crawls
Posted on May 11, 2014
(Last modified on August 7, 2020)
| 1 minutes
| Kinshuk Chandra
A rubber string is 10 meters long. A worm crawls from one end to the other at 1 meter/hr. After each hour the string stretches to become 1 meter longer than it’s last length.Will it reach the end ?
Solution Yes, the worm will reach the end because at the end of every hour when rubber band stretches, the distance travelled by the worm in past hr(s) will also increase and remaining distance to travel becomes less as compared to earlier.
[Read More]