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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  
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  
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:  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  
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  
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  
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  
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  
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  
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 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  
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  
Caesar and Brutus Games puzzles  Weight: 5 Liked the puzzle: 100% 26.12.2009
Two commanders (Caesar and Brutus) conquer a country which forms a connected graph with nodes representing cities and edges representing roads. First, Caesar chooses a city and claims it. Then, Brutus claims any of the remaining cities. Turn by turn, the commanders claim the available cities that are adjacent to the cities they have already claimed. If a commander cannot make a claim, he skips a move. The game continues until all cities have been claimed. Both commanders wish to claim a maximal number of cities. Can Brutus win in this game?
Comments:  5 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  



 
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