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  
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  
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 balls Weighing puzzles  Weight: 1 Liked the puzzle: 100% 03.02.2011
A Megamind has ordered a set of steel balls for his scientific experiments: 2 red, 2 orange, 2 yellow, 2 green, and 2 blue. The order was fulfilled but the balls of some color were made 1g lighter than the others. The Megamind has a balance scale that shows the exact weight differential between the two cups. He needs to determine the defective color using one weighing. Please, help the Megamind to do this.
Comments:  1 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  
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  
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  
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  
50 coins Logic puzzles  Weight: 3 Liked the puzzle: 100% 27.12.2009
Once upon a time, a tsar was holding a reception and the Megamind was among the guests. The tsar decided to test how smart the Megamind was, took him into a dark room, and gave the following task: On the table in this room, there are 50 coins, exactly 10 of them are tails up. In the darkness, it is impossible to determine the sides of these coins. Touching the coins also does not help. The Megamind has to separate these coins into two groups so that the number of tails in both are equal. Can he do it?
Comments:  4 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  
A sequence Patterns and correspondences  Weight: 4 Liked the puzzle: 100% 03.02.2010
1. Continue the sequence a, aa, ba, abaa, aaabba, cabbaa, ... 2. Could symbol "d" eventually appear in this sequence?
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  
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 foreign sentry Knights, Knaves and Jokers  Weight: 5 Liked the puzzle: 100% 04.01.2010
You are standing at the road fork. One of the two roads leads to your destination, but you don't know which one. Fortunately, there is a sentry guarding the intersection. Unfortunately, the sentry can be a knight or a knave, moreover, he is a foreigner. He understands you, but when he responds, he says "uhh" or "err" meaning "yes" or "no", but you don't know what means what. He does not say anything else, and he is standing at attention, not being able to point in the right direction. On top of all this, the sentry is somewhat dumb, i.e. he cannot understand sentences longer than 13 words. You may ask a single question to figure out which way to go. Which question should you ask?
Comments:  1 check your solution  
The telephone cable 2 Geometry puzzles  Weight: 5 Liked the puzzle: 100% 01.01.2010
The Megamind has a square parcel of land of size 1x1 km. Accidentally, he has found out that the devious Occupants had buried a telephone cable through his land and use it for their devious communications. The cable is buried along a straight line crossing the square land plot. After discovering this, the Megamind got his shovel and... paused to think. What is the shortest trench that the Megamind has to dig to find the cable? The trench may be disconnected. The proof of optimality is not required.
Comments:  3 check your solution  
A game with three dice Logic puzzles  Weight: 5 Liked the puzzle: 100% 26.12.2009
A MegaMind has three dice whose faces are marked with numbers 1,..,6. Some numbers can be repeated. He offers to play the game in which his opponent can choose any die, and the MegaMind will choose one of the remaining two. Then they discard the last die, and start rolling. Whoever rolls a lower number, pays the opponent a predetermined sum, say $1. In case of equality, the MegaMind lose. How did the MegaMind mark the dice if it is known that he plays this game nearly every day, and usually wins?
Comments:  3 check your solution  



 
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