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 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  
Six glasses Puzzles for children  Weight: 1 Liked the puzzle: 100% 22.01.2011
A row of six glasses is on a table. Three full glasses are followed by three empty glasses. Is it possible to make these glasses alternate: full,empty full, etc by touching only one glass?
Comments:  3 | 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  
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  
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  
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  
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  
A circle of lies Knights, Knaves and Jokers  Weight: 4 Liked the puzzle: 100% 16.01.2010
After a shipwreck, a MegaMind found himself on an island where some natives always lie and some always tell the truth. As a ritual, all natives stood in a circle facing the center, joined their hands and everybody told the MegaMind whether his right hand side neighbor is a liar or a truth-teller. Based on this information, the MegaMind was able to determine the exact percentage of natives that tell the truth. Can you also determine this percentage?
Comments:  2 | check your solution  
A Megamind in a boat Geometry puzzles  Weight: 4 Liked the puzzle: 100% 27.12.2009
A Megamind is sitting in a boat at the center of a circular lake of radius R. On the lake shore, an evil Goblin awaits. Luckily for the Megamind, the Goblin can only move along the shore. Unfortunately, the Goblin is 4 times as fast as the Megamind in his boat. The Megamind can save himself if he gets to the shore and evades meeting with the Goblin. Can the Megamind save himself? If yes - how?
Comments:  1 | check your solution  
A game with coins Games puzzles  Weight: 4 Liked the puzzle: 100% 12.03.2011
Two Megaminds play a game: they have a regular round table and an unlimited supply of identical round coins. Turn by turn, they place coins on the table until someone can no longer make a move. The coins cannot overlay each other, but they can touch. Who has a winning strategy (and what is it) in this game?
Comments:  6 | check your solution  
A thousand natives Knights, Knaves and Jokers  Weight: 5 Liked the puzzle: 100% 30.12.2009
A MegaMind was captured and brought to an island where a 1000 natives live. Some natives always tell the truth and some always lie. There is at least one truth teller on the island. The MegaMind was promised to be kept alive if he can point out the liars from the truth-tellers. Every hour, the MegaMind is allowed to call up a number of natives and ask a single question: "How many of you are truth-tellers?" or "How many of you are the liars?" How many hours does the MegaMind need before he can determine the liars/truth-tellers?
Comments:  7 | check your solution  
10101...01 Algebra, arithmetic  Weight: 5 Liked the puzzle: 100% 07.02.2010
For which values of n, the decimal number 10101..01 (the alternating sequence of n ones and n-1 zeros) is a prime?
Comments:  1 | check your solution  
Ladders with missing steps Logic puzzles  Weight: 5 Liked the puzzle: 100% 17.01.2010
To fix his roof, Megamind needs to climb up a ladder. He has found many ladders to choose from, but unfortunately some of them were missing steps. Megamind cannot climb a ladder if it is missing two or more steps in a row. Originally, all ladders had N steps, marked bottom to top. How many different ladders can Megamind climb?
Comments:  3 | check your solution  



 
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