Hard Puzzles And Riddles

100 Blue Eyes Puzzle

Puzzle: This puzzle is one of the hardest puzzle in the world. If you are able to solve this, believe me you are genius. A group of people with assorted eye colors live on an island. They are all perfect logicians — if a conclusion can be logically deduced, they will do it instantly. No Read More →

Rope Escape Puzzle

Puzzle: Jim is trapped at the top of a building which is 200m high. He has with him a rope 150m long. There is a hook at the top where he stands. Looking down, he notices that midway between him and the ground, at a height of 100m, there is a ledge with another hook. Read More →

Possible Paths across a Rectangular Grid

Rectangular Grid

Problem: Consider a rectangular grid of 4×3 with lower  left corner named as A and upper right corner named B. Suppose that starting point is A and you can move one step up(U) or one step right(R) only. This is continued until B is reached. How many different paths from A to B possible ? Now let’s Read More →

Chasing Dog Puzzle

Puzzle: There are four dogs each at the corner of a unit square. Each of the dogs starts chasing the dog in the clockwise direction. They all run at the same speed and continuously change their direction accordingly so that they are always heading straight towards the other dog. How long does it take for the Read More →

Crossing the Bridge Puzzle

Crossing the Bridge riddle

Puzzle: Four people need to cross a rickety bridge at night. Unfortunately, they have only one torch and the bridge is too dangerous to cross without one. The bridge is only strong enough to support two people at a time. Not all people take the same time to cross the bridge. Times for each person: Read More →

Inverted Cards Puzzle

Problem: One day, Santa and banta were playing cards, but suddenly power went off. Santa randomly inverted position of 15 cards out of 52 cards(and shuffled it) and asked banta to divide the card in two piles with equal number of cards facing up. It was very dark in the room and banta could not Read More →

Blind bartender’s problem


Problem: Four glasses are placed on the corners of a square table. Some of the glasses are upright (up) and some upside-down (down). A blindfolded person is seated next to the table and is required to re-arrange the glasses so that they are all up or all down, either arrangement being acceptable, which will be Read More →

Sand Timer Puzzle

Sand timer

This Puzzle is one of the most commonly asked interview puzzle. Problem: You have two sand timers with you. One can measure 7 minutes and the other sand timer can measure 11 minutes. This means that it takes 7 minutes for the sand timer to completely empty the sand from one portion to the other. Read More →

3 Mislabeled Jars

3 mislabeled jars of Apple and Orange

Puzzle: This problem is also called Jelly Beans problem. This is the most commonly asked interview puzzle. You have 3 jars that are all mislabeled. One jar contains Apple, another contains Oranges and the third jar contains a mixture of both Apple and Oranges. You are allowed to pick as many fruits as you want Read More →

3 Bulbs and 3 Switches

3 bulbs and 3 switches puzzle

This puzzle is perhaps not as ‘pure’ as the others, it doesn’t reduce to a mathematical model. But it is quite a common question asked in interviews so it’s worth looking at it… Problem: You are in a room with 3 switches which correspond to 3 bulbs in another room and you don’t know which Read More →

25 horses and 5 lanes

25 horse and 5 lanes puzzle

Problem: There are 25 horses and 5 lanes. You have no idea about which horse is better than other. Find in minimum possible races, the first three fastest running horses. Solution: We will have 5 races with all 25 horses Let the results be u1,u2,u3,u4,u5 v1,v2,v3,v4,v5 x1,x2,x3,x4,x5 y1,y2,y3,y4,y5 z1,z2,z3,z4,z5 Work through a process of elimination: Read More →

100 Doors Puzzle

100 doors toggle puzzle

Puzzle: : You have 100 doors in a row that are all initially closed. you make 100 passes by the doors starting with the first door every time. the first time through you visit every door and toggle the door (if the door is closed, you open it, if its open, you close it). the Read More →