Welcome to MindCipher, a social repository of the world's greatest brain teasers, logic puzzles and mental challenges.

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 7 Tea and Wine You take a spoon of wine from a barrel of wine and put it into your cup of tea. Then you return a spoon of the (non-uniform) mixture of tea and wine from your cup and put it in the barrel. Now you ha ... Submitted by Ravi Doable 4.7 6 What Number Is It? So there are two students, that play a game with their teacher. They have 10 cards, each card is numbered 1,2,3,...,9,10. And then their teacher gives them two cards that is consecutive. For example, o ... Submitted by Rifqi Ardia Ramadhan Easy 2.7 5 Matchsticks This is a classic Martin Gardner puzzle. See the picture - the four matchsticks represent a martini glass and the match head represents an olive. Move just two matches so that the glass is reformed bu ... Submitted by Aakash Doable 3.6 5 Clock Hands - Google Interview Question How many degrees are there in the angle between the hour and minute hands of a clock when the time is a quarter past three? Submitted by Valentin Doable 3.5 5 The Stealing Mailman This is a fairly simple problem that can cause some people trouble. Kevin and Sophia want to mail high confidential letters between each other. They know that the mailman is crooked and opens the le ... Submitted by Ravi Doable 6.5 5 Age of Three Kids One day, a guy from census come into a house. When he rings the bell, a lady comes out. He then asks how many people lives in her house, and their age. And then she says: I am 45 years old. I have thr ... Submitted by Rifqi Ardia Ramadhan Doable 6.0 4 Don't Mate in One This problem was first publicized by Karl Fabel, a German chess problemist. Find a move for white that will not result in an immediate checkmate of the black king. Submitted by Aakash Doable 6.6 4 Balloon Business You’re sitting in a stationary car. There’s a helium balloon tied to its floor. You accelerate and, obviously feel like you’re being pushed backwards (against the direction of your acceleration). W ... Submitted by Valentin Doable 4.0 4 Time To Fuse You have a string-like fuse that burns in exactly one minute. The fuse is inhomogeneous, and it may burn slowly at first, then quickly, then slowly, and so on. You have a match, and no watch. How do ... Submitted by Valentin Doable 4.5 1 Neat twist on hat problem! There are 100 people standing in a circle. Each person is given one hat to wear. A hat is either colored red or blue. A person cannot see his own hat color, but he can see the colors of the hats of all ... Submitted by Simon Doable 6.0 1 4 buttons and a light bulb There are two rooms, in one room there is a light bulb, and in the other there is a round table, with 4 buttons arragned in a square on it. Each button may be on or off, and the light bulb will be on o ... Submitted by TulkinRB Hard 8.0