BrainDen.com - Brain Teasers

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## Popular Content

Showing content with the highest reputation since 08/11/18 in all areas

1. 1 point

LEGEND
2. 1 point

## Massive multiplication

n factorial (represented as n!) is the product of all positive integers up to n. So the number you are looking for is 1,000,000! ("one million factorial")
3. 1 point

## Walking, running, driving, waiting

I'll accept it but I was thinking more like ....
4. 1 point

## Walking, running, driving, waiting

With a tip of the hat to @BMAD for his interesting puzzle. For your amusement, here's an interesting spin on this genre: One night you encounter a two-hour traffic delay due to an accident (the tow truck had difficulty clearing the road.) So, for a time interval 13 of two hours you were constrained to travel at 0 mph. You called home and said, sorry dear, but I'll be two hours late getting home. The next night, for some unimaginable reason, you were also constrained to travel part of the way at 0 mph, this time for a distance of one inch. What do you say now when you call home?
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6. 1 point

## The Pebbles

We are in a TV game. We have 8 same looking boxes, each of which has 2 pebbles. Each pebble could be either precious or not precious. We choose a box and the host, without looking inside the box, pulls out a pebble. It comes out to be precious. The TV host then declares that we have exactly 50% chance that the 2nd pebble inside the box is precious, too. If we know that, in the beginning of the game, the count of precious pebbles is no less than the count of not precious pebbles, which of the statements MUST be true? We assume that the TV host knows the pebbles distribution in the boxes - in what amount of boxes the precious pebbles are 0,1 or 2. The TV host, however, doesn't know the kind of pebbles in each specific box, as he himself doesn't differ the boxes from one another. 1. If we swapped the boxes, we would have higher chance of picking up precious pebble next. 2. If we swapped the boxes, we would have same chance of picking up precious pebble next. 3. If we swapped the boxes, we would have lower chance of picking up precious pebble next. 4. In the beggining of the game, there've been exactly 2 boxes with 2 precious pebbles each. 5. In the beginning of the game, half the boxes have had 1 precious and 1 not precious pebble. 6. In the beginning of the game, the precious and not precious pebbles have been equal in count. 7. In the beginning of the game, the amount of boxes with 2 precious pebbles is equal to the amount of boxes with 2 not precious pebbles. 8. The TV host has gone wrong. There's no way that there's 50% chance for 2nd precious pebble in our box, as there is unequal amount of pebbles left in the game. 9. None of the above must be true.
7. 1 point

## Nameless Riddle

Well THAT fell fast!
8. 1 point

## 12 chess pieces

Question about #13, which sounds to me like a conflict. should it read “ nothing is south of the one black rook, which is on the edge”? or should it read “ nothing is south of the white rook that is on the edge” or even “one of the white rooks is on the edge, and has nothing south of it”? for that matter, should it name a different piece than white rook?
9. 1 point

## DUCK

Son, father and grandfather - three only
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11. 1 point

## shuffling algorithm for letters in a word

It looks like you're taking the first letter and essentially rotating it through the different positions while the other letters remain in the same order. I noticed that all the possible permutations begin with two letters that were next to each other in the original sequence (or in the first and last spot). For example, I don't think you can get a sequence starting with AC. So this does not seem to hold up.
12. 1 point

## Smallest Grid to Fit 1 2 3 4 5 6 7 8 9 0

so far just 2
13. 1 point

## A Dutiful Riddle

An oldie but a goody (IMO): ****************************** Five-walled open house Shut my door and make it four. I know exactly who you are, Where you sleep, friends you keep. A loyal soldier out on tour I take my leaves overseas. So pin the gold upon my breast, Give me orders crossing borders.
14. 1 point

## A Dutiful Riddle

Wait a minute, wait a minute, Mr
15. 1 point

## Burning Riddle

But off Course! : )
16. 1 point

## Burning Riddle

Though seldom seen, I'm world renowned Ever in flight above the ground. Teeth chewing, gnashing in time gnawing on knots, shunning the find. My hands at the ready, arms at the stay Heart like the sun, burning away. Ears like a rabbit's, pinned to the side-- Listening close, far and wide.
17. 1 point

## Burning Riddle

Are you a .....
18. 1 point

## An Acrobatic Riddle

I’m the acrobat at your command, Give me a turn, or put me on the stand. I’m the sentinel, doorman you need, Give me a go, a go-ahead from me. Hit me, poke me, nail me in your wake, Without my flips, weak knees would quake. I live in one state and travel to another, Sunny side up or fumble in the other.
19. 1 point

20. 1 point

## Mouse & Cheese Cube

The answer should be 25. My "proof" is a brute force programming solution. I have a psuedocode c++ bruteforce solution. I can give the full version if requested. It takes a few seconds to brute force all possible paths. This might count as a proof, depending on if you trust the computer to be reliable. Basically what it does is it generates all possible paths, and then prunes as it goes along so the program dosen't take basically forever, or 6^27 moves. Now a proof will involve some theorems in graph theory, which I don't yet know all that well. Assume the XYZ plane void recursive_dumb_solution( A 3D cube,Position of X, Y, and Z of current spot,direction it went twice ago, direction it went to get here){ if traveled along a direction twice in a row, return to the above function. else if( x<0 || x > 2 || y < 0 || y > 2 || z < 0 || z > 2) AKA if it exited the cube, return. else if(cube[x][y][z] == 1) AKA if visited spot already visited, then return. else{ //mark the current position of the cube as visited. cube[x][y][z] = 1; /////Moves in every direction possible. recursive_dumb_solution(cube, x+1, y, z, length+1,'x',prev_dir); recursive_dumb_solution(cube, x-1, y, z, length+1,'x',prev_dir); recursive_dumb_solution(cube, x, y+1, z, length+1,'y',prev_dir); recursive_dumb_solution(cube, x, y-1, z, length+1,'y',prev_dir); recursive_dumb_solution(cube, x, y, z+1, length+1,'z',prev_dir); recursive_dumb_solution(cube, x, y, z-1, length+1,'z',prev_dir); cube[x][y][z] = 0; return; } }
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22. 1 point

## I'm Back

Greetings, my name is Cody and I am new here in this forum. Nice meeting you all. Although I have never heard of it, I am actually quite curious about what it is!
23. 1 point

## Good-natured Trump jokes

A joke from the internet yesterday: Trump really delivered when he said he would run the government just like his businesses. It's already shutdown! Don't worry, he still has three years to bankrupt it.
24. 1 point

## 1000 people in a circle

Assuming N people, the last standing (S) is given by: S=2*(N-2^m)+1, where m=floor[ln(N)].
25. 1 point

## Ex-gifted trying to get smart again

Doesn't look like people get many responses in this section but I will introduce myself anyway. I'm a 36-year-old mom. I used to be smart, a long time ago. Was in the gifted program throughout grade school. Battled severe psychological problems starting in high school and am still battling them today. My grades in high school and college were pretty bad and I dropped out of pre-med. My younger sisters (who were not "gifted") have achieved much more academically and professionally than I have. Which is fine, because I like my life. But, sometimes I miss people telling me I'm smart! SO, I have started playing around with Mensa-type puzzles in an attempt to stretch my brain. I'm not having a lot of luck so far-- which is why I'm here.
26. 1 point

## I'm not a rebellious missionary

Right on, PG, and glad you like it. This one I think I'll keep in a Sundae Best collection.
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28. 1 point

## I swear:

I swear: 1) To strangle the next person who uses 'suicide' as a verb. 2) That if I offended or hurt you in any way, I didn't mean it. 3) That I'll stop procrastinating. Tomorrow. Add whatever you swear.
29. 1 point
I have just created Homework Help forum. I have also started the first topic to list all members willing to help. Read the rules and feel free to ask questions and help others to find solutions/answers. Enjoy!
30. -1 points

## Atlas

Hi guys, I love riddles so much that I wanted to insert it in game me and my friend are making. The game is 2D RPG roguelike survival game happening in a randomly generated universe. Here is the fun part, one of the random encounters will be the character in a game that will approach the player and ask him a riddle. If a player answers correctly he will be awarded else Riddler will attack the player. (About 10% of NPC encounters in the game will be by riddler). I think that's the cool way to promote riddles and make kids (and grownups) use the brain. Also please write me some riddles and I will insert it in game. Thank you, Josip
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