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  
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:  1 | check your solution  
A 100 M&Ms Puzzles for children  Weight: 1 Liked the puzzle: 100% 02.01.2010
A Megamind has two bags and 100 M&Ms. He needs to put all the candies into the bags so that one bag has twice as many M&Ms as the other. He cannot split the M&Ms. What should the Megamind do?
Comments:  11 | 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  
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  
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 farther, 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 the 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  
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  
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  
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  
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  
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  
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  
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 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  
Correct labels Weighing puzzles  Weight: 5 Liked the puzzle: 100% 08.01.2010
There are six weights 1,2,3,4,5,6 grams. They are labeled with numbers 1,2,3,4,5,6. Some may be mislabeled. How can you determine whether all labels are correct using a balance scale? What is the minimal number of weighings?
Comments:  1 | check your solution  
A game with sums Games puzzles  Weight: 5 Liked the puzzle: 100% 03.01.2010
Two players play the following game. An even number of cards are arranged in a row. Each card is marked with a real number. Upon his turn, a player takes a card from either end of the row. Whoever collects the greater sum is a winner. Otherwise, a draw is declared. Which player is guaranteed not to lose? What is his strategy?
Comments:  5 | check your solution  



 
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