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Numbers in a square Patterns and correspondences  Weight: 1 Liked the puzzle: 75% 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  
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 incense sticks Logic puzzles  Weight: 1 Liked the puzzle: 100% 27.12.2009
You have two incense sticks, that burn unevenly, and a lighter. Each will burn for an hour. How can you time 45 minutes using nothing but these tools.
Comments:  3 | check your solution  
Numbers on the fence Patterns and correspondences  Weight: 2 Liked the puzzle: 100% 31.12.2009
A Megamind walked along a fence and discovered strange pairs of numbers. First, he saw "188->4". A bit fаrther, he discovered "232->0". A few steps after that, "100->2". Then, "163->1". Then he saw a little boy who was just beginning to paint something. When the Megamind called a boy, he ran away. Approaching the site, the Megamind saw an incomplete pair "386->...". He took out his favorite marker and completed the pair. What number did he write?
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  
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  
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  
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 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:  5 | 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  
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  
18 crystals Weighing puzzles  Weight: 5 Liked the puzzle: 100% 30.12.2009
Once upon a time, a Megamind worked as an optometrist for an Occupier who was color blind. The Occupier had a dream that he may regain perfect vision if the Megamind made him a set of 9 red and 9 blue crystals. The crystals should be of the same size, but the blue ones should be heavier than the red ones. Crystals of the same color should weigh the same. The Megamind completed the order and brought two sets of crystals: blue in his right hand and red in the left. The Occupier was suspicious, he did not trust the Megamind. Fortunately, the Occupier has a balance scale. How can the Megamind convince the Occupier that all crystals in one hand are blue and in the other - red. He can use no more than three weighings.
Comments:  5 | 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  
A game with wooden sticks Games puzzles  Weight: 5 Liked the puzzle: 100% 02.01.2010
Two MegaMinds play a game with 100 wooden sticks. The lengths of the sticks are 1,2,3,...,100 inches. Turn by turn, the players choose three of the remaining sticks which form a triangle, and burn them. The player that cannot make a move loses. Which player has a winning strategy (justify your answer)?
Comments:  3 | check your solution  



 
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