Brain games: puzzles, riddles, and logical games.
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Numbers in a square Patterns and correspondences  Weight: 1 Liked the puzzle: 80% 24.12.2011
Place numbers 1,2,.., 9 without repetitions into a 3x3 square so that the sums in all rows, columns, and diagonals are all equal.
Comments:  1 check your solution  
Links and chains Logic puzzles  Weight: 1 Liked the puzzle: 100% 02.04.2011
Once upon a time, a Megamind worked as a smith. He was brought 5 chains each consisting of 3 links. What is the minimal number of links that the Megamind should re-lock to make one long chain?
Comments:  1 check your solution  
States and characters Patterns and correspondences  Weight: 1 Liked the puzzle: 100% 26.01.2010
Florida - n, New York - r, Texas - n, Washington - ?
Comments:  1 check your solution  
Defective pixel Algebra, arithmetic  Weight: 1 Liked the puzzle: 100% 03.01.2010

There is true expression on panel. But only one pixel is defective. Which one?

Press for see in full size.
Comments:  1 check your solution  
Two villages Knights, Knaves and Jokers  Weight: 2 Liked the puzzle: 100% 27.12.2009
A Megamind is lost in the mountains. He is standing on a path, shouting for help. Finally, he sees a local approaching. Megamind knows that the locals can be knights that always tell the truth, or knaves that always lie. He also knows that the path leads to the village of knights in one direction and to the village of knaves in the other. The problems is that the knaves are also hateful of Megaminds, and will stone him if gets to their village. How can Megamind ask one question and determine the right way to go?
Comments:  4 check your solution  
Milk, lemonade, water, and coke Patterns and correspondences  Weight: 2 Liked the puzzle: 100% 27.01.2011
A bottle,a glass, a carafe, and a can contain milk, lemonade, water, and coke. Water and milk are not in the bottle. The container with lemonade is immediately between the carafe and the container with coke. The can does not contain lemonade or water. The glass is next to the can and the container with milk. The containers form a row. How exactly are they arranged?
Comments:  4 check your solution  
Obtain 24 Algebra, arithmetic  Weight: 2 Liked the puzzle: 100% 27.12.2009
Using numbers 1,3,4,6, and basic arithmetic operations (addition, subtraction, multiplication, and division) and parentheses, obtain and expression that evaluates to 24. You may use only these numbers and only these operations. Every number should be used exactly once. Numbers cannot be concatenated, i.e. you cannot use 13 or 146.
Comments:  7 check your solution  
101 coins Weighing puzzles  Weight: 3 Liked the puzzle: 100% 04.01.2010
Among 101 coins, exactly 50 are counterfeit. A counterfeit coins weighs one gram more or gram less than the real coin (counterfeit coins may weigh differently). You have a balance scale that shows the exact weight differential between the two cups. How can you determine whether a given coin from this set is counterfeit using the scale only once?
Comments:  1 check your solution  
The fifth number Algebra, arithmetic  Weight: 3 Liked the puzzle: 100% 09.01.2010
The set of numbers 1,3,8,120 has a remarkable property: the product of any two numbers is a perfect square minus one. Find a fifth number that could be added to the set preserving its property.
Comments:  4 check your solution  
Weights Weighing puzzles  Weight: 3 Liked the puzzle: 100% 29.01.2010
What is the minimal number of weights required to be able to balance all integer weights 1,2,...,40 on a balance scale? Justify the minimality.
Comments:  4 check your solution  
12 coins Weighing puzzles  Weight: 4 Liked the puzzle: 100% 03.02.2010
A Megamind has 12 coins, one of which is counterfeit and weighs differently from the others. He has a balance scale, but no weights. How can the Megamind find the counterfeit coin and determine whether it is lighter or heavier than the standard ones? What is the minimal number of weighings required?
Comments:  1 check your solution  
A game of symmetry Games puzzles  Weight: 4 Liked the puzzle: 100% 17.03.2011
Two megaminds play a game on a board sized 1x81 cells. The board is initially empty. At each turn first megamind can place a stone (either black or white) in any cell. Second megamind can either swap any two stones or skip a turn. After megaminds made 81 turns each, the symmetry of the board is assessed. If the stones are located symmetrically, second megamind wins, if not - first one wins. Who will win and why?
Comments:  1 check your solution  
Six matches and triangles 2 Geometry puzzles  Weight: 4 Liked the puzzle: 100% 07.02.2010
How to make one equilateral and three isosceles (and not equilateral!) triangles using 6 sticks of the same length? Sticks cannot be broken and/or laid over each other and no free ends of the matches may be left.
Comments:  1 check your solution  
Guess your color Logic puzzles  Weight: 5 Liked the puzzle: 100% 26.12.2009
Three MegaMinds enter a room, one by one. Upon entrance, each MegaMind is given a hat that can be white or black. Each MegaMind can see the other two hats, but not his own. After they have spent 5 minutes in the room, the MegaMinds are separated and asked the following question: "What is the color of your hat?" They can say "black" or "white" or simply refuse to answer. If nobody answers or if somebody gives a wrong answer, they will spend the rest of their lives in a dungeon. What should each MegaMind do? What are the chances that they will be set free? There is no preliminary agreement or exchange of any information among them.
Comments:  5 check your solution  
A game with sums Games puzzles  Weight: 5 Liked the puzzle: 100% 03.01.2010
Two players play the following game. An even number of cards are arranged in a row. Each card is marked with a real number. Upon his turn, a player takes a card from either end of the row. Whoever collects the greater sum is a winner. Otherwise, a draw is declared. Which player is guaranteed not to lose? What is his strategy?
Comments:  5 check your solution  
Divide a parallelogram Geometry puzzles  Weight: 5 Liked the puzzle: 100% 02.04.2011
How to divide a parallelogram into 9 isosceles triangles?
Comments:  1 check your solution  



 
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