You are blindfolded and 10 coins are place in front of you on table. 5 are having their heads-side up and 5 are having their tails-side facing upward. You cannot tell which way they are by touching the coin. You are allowed to touch the coins and flip them as many times as you want. How […]

There are 10 prisoners are in 10 different cells of a prison. There is no way in which they can communicate with each other. Each night, the warden picks one of the 10 prisoners and that prisoner is supposed to spend the entire night in the central living room. There is one bulb in the living […]

Four glasses are placed on the four corners of a square rotating table. Each glass is either upright (up) or upside-down (down). You have to turn all the glasses in same direction (either all up or all down). There are following conditions You are blindfolded, At one time you can only change two glasses (and […]

You are standing before two closed doors. One of the doors leads to heaven and the other one leads to hell. Two watchmen are standing, one in front of each door. You know one of them always tells the truth and the other always lies, but you don’t know which watchman tells the truth and who is the liar. […]

You have some work to be done by a worker in 7 days. The worker need to be paid every day after his work. The total cost of the work of 7 days is one gold bar (so every day the worker must be paid 1/7’th of the bar). You have only one gold bar, and […]

How many points are there on the globe, so that if you walk 1km south, then 1km east and then 1km north, you reach the place where you started.

There are twenty five horses and you can conduct a race of only five horses at one time. There is no way to find out the absolute speed of a horse (we only know there relative speed). At least how many races will it take to determine the three fastest horses?

There are 5 pirates, A, B, C, D and E. They have a strict hierarchy, A is senior to B, B is senior to C, C is senior to D and D is senior to E. So it is like (A > B > C > D > E). These pirates have 1000 gold coins […]

There are 50 bikes, each with a tank that has the capacity to go 100 kms (when the fuel is full). Fuel tanks of all the bikes are full. Using these 50 bikes, what is the maximum distance that you can go?

Earlier we discussed, how to calculate total number of squares (of all sizes) on the chess board. Here, the problem is, How many rectangles (of any size) will be there on the chess board?