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  
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  
Vases and beads Patterns and correspondences  Weight: 1 Liked the puzzle: 100% 24.12.2011
A Megamind on his treasure hunt discovered a cave with six ancient vases. Unfortunately, instead of treasures, the vases contained beads. The first vase had 60 beads, the second had 30 beads, the third had 20 beads, and the fourth had 15 beads. How many beads were in the fifth and the sixth vases, given that these number form a certain pattern?
Comments:  2 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  
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  
One more opening Chess puzzles  Weight: 3 Liked the puzzle: 100% 24.12.2011
Starting from the initial possition White and Black have done 4 moves each. What are these moves? Picture.
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  
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:  10 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 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  
Rabbits in the store Algebra, arithmetic  Weight: 5 Liked the puzzle: 100% 09.02.2011
In a pet store, the first Megamind bought two plus a half of the remaining rabbits. The second Megamind bought three plus a third of the remaining rabbits. The third Megamind bought four plus a fourth of the remaining rabbits. At some point, one of the Megaminds could not make his purchase. What is the maximal number of satisfied customers (Megaminds)?
Comments:  3 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  
Mad Max 2 Logic puzzles  Weight: 5 Liked the puzzle: 100% 29.01.2010
A circular road in a desert is 100 miles long. Some finite number of barrels are placed randomly along the road. These barrels contain a total of 100 liters of gasoline, but otherwise each barrel contains a random amount of gas. A car takes 1 liter of gas per mile. Can Mad Max (the driver) travel the entire circle in either direction if his car has an empty gas tank? He may start from any barrel.
Comments:  1 check your solution  



 
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