
1. 
pretorik 
 
161 
2. 
markr 
 
116 
3. 
Gordon Weir 
 
104 
4. 
mbloomfi 
 
97 
5. 
Dennis Nazarov 
 
96 
6. 
zzz123 
 
72 
7. 
Srikanta 
 
56 
8. 
lidSpelunker 
 
53 
9. 
SAMIH FAHMY 
 
48 
10. 
jkr 
 
44 




1. 
denisR, mishik 
 
236 
2. 
alan, De_Bill 
 
231 
3. 
dddfff 
 
228 
4. 
kavfy 
 
221 
5. 
idler_ 
 
106 
6. 
akajobe 
 
94 
7. 
tolstyi 
 
56 
8. 
STARuK 
 
42 
9. 
vale 
 
31 
10. 
xandr 
 
11 





A certain type of bacteria double every second. If we put one bacterium in a Petri dish, the dish will fill in 1 minute. How long will it take to fill the dish, if we start with 2 bacteria? 


Puzzle statistics "Bacterium".
Last updated 6328948.4 minutes ago.

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There is true expression on panel. But only one pixel is defective. Which one?



Puzzle statistics "Defective pixel".
Last updated 6328948.4 minutes ago.

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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. 


Puzzle statistics "Obtain 24".
Last updated 6328948.4 minutes ago.

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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. 


Puzzle statistics "The fifth number".
Last updated 6328948.4 minutes ago.

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The 40th anniversary tournament 
Algebra, arithmetic 

Weight: 5 

Liked the puzzle: 100% 

05.01.2010 

Once upon a time, grandfather Megamind told his grandchildren the following tale: On the 40th anniversary of their town, a soccer tournament was held in the central park. Five teams played with each other, 3 points were given for a win, and 1 point was given for tie. Each team earned a different number of points. The goal total was 40. But most curiously, a team placed higher scored fewer and gave up more goals than a team placed lower. Could such tournament really have taken place or is it possible that the old Megamind finally felt his age? 


Puzzle statistics "The 40th anniversary tournament".
Last updated 6328948.4 minutes ago.

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For which values of n, the decimal number 10101..01 (the alternating sequence of n ones and n1 zeros) is a prime? 


Puzzle statistics "10101...01".
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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)?



Puzzle statistics "Rabbits in the store".
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Once upon a time, 23 Megaminds decided to play a soccer game. In the process of choosing teams, they observed a curious property: no matter who was elected as a referee, the remaining 22 players could be split into two teams with equal total weight. Is it possible that not all Megaminds weighed equally? Each Megamind weighed an integer number of kilograms. 


Puzzle statistics "The players' weights".
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Prove that the sum of all divisors of a nonzero square integer is odd. 


Puzzle statistics "Sum of all divisors of a square".
Last updated 6328948.4 minutes ago.

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