Brain games: puzzles, riddles, and logical games.
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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  
8 coins Weighing puzzles  Weight: 1 Liked the puzzle: 100% 30.12.2009
You have 8 coins that appear to be identical, except one (which is counterfeit) is slightly heavier than the others. What is the minimal number of weighings on the balance scale that is required to find the counterfeit coin?
Comments:  0  
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:  0  
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:  1  
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:  0  
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:  0  
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:  0  
The mouse hunt Games puzzles  Weight: 4 Liked the puzzle: 100% 11.01.2010
A smart cat named Leopold is hunting a mouse. A mouse is hiding in one of five holes arranged in a row. Leopold can reach into one of the holes and try to catch the mouse. If he is not successful, the scared mouse runs into a right/left neighboring hole. Is it guaranteed that Leopold will catch the mouse? If so, what should he do?
Comments:  0  
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:  0  
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:  0  



 
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