BrainDen.com - Brain Teasers

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## Popular Content

Showing content with the highest reputation since 01/03/17 in all areas

1. 1 point

## Mouse & Cheese Cube

Hopefully this one has not appeared before... Suppose 27 identical cubical chunks of cheese are piled together to form a cubical stack, as illustrated below. What is the maximum number of these cheese chunks through which a mouse of negligible size could munch before exiting the stack, assuming that the mouse always travels along the grid of 27 straight lines that pass through the centers of the chunks parallel or perpendicular to their sides, always makes a 90 degree turn at the center of each chunk it enters, and never enters any chunk more than once?
2. 1 point

## A bug problem

Sorry, something got lost in copying and pasting. The site does not like the formatting used in word, so I am attaching a picture of the solution ... apologies in advance.
3. 1 point

4. 1 point

## Forgotten District II Mafia

@flamebirde because Molly was playing off of the word easy, which is a popular Commodores song. No other reason
5. 1 point

## Forgotten District II Mafia

Edit - double post, so I thought I'd take this time to post a dancing monkey gif. Enjoy.
6. 1 point

Player A has one more coin than player B. Both players throw all of their coins simultaneously and observe the number that come up heads. Assuming all the coins are fair, what is the probability that A obtains more heads than B?
7. 1 point

## Hard riddle

(BR / BL +UR) UL Thus... (8/4 +2) 3= 12 (2/1 + 6) 4= 32 (9/3 +4) 2= 14 and for the last one.. (6/2 +3) 5 = 30
8. 1 point

## Signups for Forgotten District II Mafia

On my phone, I see a link on each post that says "quote". I can sort of copy and paste the roster on phone but as I found out last game, the cursor had an unfortunate habit of moving... Spoilers and colors on phone have to be done with the [ ] codes. Spoiler: {spoiler}your text here{/spoiler} with [ ] instead of { }. No spoiler titles. Colors: {color=red/orange/whatever}text here{/color} also with [ ] instead of { }.
9. 1 point

@SakuraChan
10. 1 point

## Signups for Forgotten District II Mafia

Roster: 1. maurice 2. Flamebirde 3. Molly Mae 4. 5. 6. Hirkala 7. bonanova 8. 9. 10. Roster: 1. maurice 2. Flamebirde 3. Molly Mae 4. 5. 6. Hirkala 7. bonanova 8. 9. 10. Mafia!!! Been too long! I don't know if I was supposed to leave it doubled, but I did. Hi, everyone!
11. 1 point

12. 1 point

## UN Mafia III

If it makes you feel any better, I had you and Molly as Germany and Russia before the mass outing. Thought bonanova sort of claimed Australia earlier but figured if the US killed him I'd be better off whether he was Australia or China. He seemed like the biggest threat to me with his day actions. If maurice had removed a vote besides flamebirde's, it would have been a tie and I wouldn't have even got the chance to use my RID kill. When I was first reading through, I didn't realize you were expecting me to kill Molly. Got a bit of a laugh from that. So the biggest thing the mass outing accomplished was it made sure you got China. If you had lynched fb, I would have RID killed maurice which would have been blocking. I did get really lucky with bonanova getting the UK lynched D1 so thanks for that. On another note, I came extremely close to not acting at all N2 to try to frame plasmid as Sweden. Might have given mo's claim more credibility with neither Sweden nor China showing... So now that I know asking won't get me killed, what's a PGP public key block? And where were those soft claims?
13. 1 point

## UN Mafia III

Hey guys, sorry I'm here. Didn't realize I could talk when I was trapped and then I'm having issues accessing the site on my phone. I'm on through Firefox now and it works better than Chrome I guess. I will catch up at lunch and see what I can contribute, hopefully before the night ends in case I was mercy/mod killed.
14. 1 point

## UN Mafia III

@Thalia, good points. I've played only a few Mafia games. I wish I had accepted Unreality's invite to play, back in the day, and learned it better. Coupled with a hope for a few more games to follow this one. My comfort zone is math and logic, where all the needed info is provided, just needing insight and clear thought. This is more fun, actually, and with experience I might get better. Or, I'm a very slippery guy and everything I just said is garbage. . When does the night end?
15. 1 point

## UN Mafia III

Taps watch. Oops. RIP MikeD. Would love to hear from maurice.
16. 1 point

17. 1 point

## Binary lock

Real life: I bought (very cheep) a 256MB extension card for a 80286. There were 8 dip switches and no manual. I do not know how many times each switch can be flipped, in any case, it is better to minimize the manipulation. Look https://en.wikipedia.org/wiki/Gray_code
18. 1 point

## The Donny Hall puzzle

I think phaze is right about the most practical answer. If that fails, I tend to agree with bonanova.
19. 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.
20. 1 point

## Folding paper

Agree. When I hit the send button, I realized my thinking was too simple. But instead of deleting my post (moderator privilege) I left it to take its licks.
21. 1 point

## IDENTIFY THE FAKE COIN

Divide the thirty coins into four groups of 9, 9, 9, and 3. Label the 9 coin piles as 9a, 9b, and 9c. Weighing number one is 9a vs. 9b. If they balance, the odd coin is in either in 9c or in the pile of 3. If so, then weighing Number 2 is 9a vs. 9c. If they balance, then the odd coin is in the pile of 3. Label the three coins the pile of 3 as 3a, 3b, and 3c. Weighing number 3 is 3a vs. 3b. If they balance, the odd coin is 3c. In that case, weighing number four is 3c vs. any other coin to determine if the odd coin is lighter or heavier than the rest. If after weighing No. 3, coin 3a does not balance against coin 3b, then one of them must be the odd coin. Remove the lighter coin, let’s say it’s 3b, and place coin 3c on the scale against the remaining heavier one, 3a. If they balance, then the odd coin is 3b and it is lighter. If they do not balance, then the odd coin is 3a and it is heavier. Now let’s go back and see what happens if the first weighing has a different outcome. Weighing number one was 9a vs. 9b. Let’s say that they do NOT balance. That means that the odd coin is in either 9a or 9b. Note which of the two is heavier. Let’s say 9a is heavier. Weighing number two is 9a vs. 9c. They will either balance or 9a will be heavier. There is no possibility that 9a will be lighter. If 9a and 9c balance that means that the odd coin is in 9b and that it is lighter. If 9a is again heavier, that means that the odd coin is in 9a and it is heavier than the rest. Let’s say it’s in 9a and it’s heavier. Now divide 9a into three groups of three coins each. Label them 3A, 3B, and 3C. Weighing number three is 3A vs 3B. If they balance then the odd (heavier) coin is in 3C. If they do not balance, the odd (heavier) coin is in the heavier of 3A or 3B. Take the group of the three that contains the odd coin and divide it into 3 individual coins: 1a, 1b, and 1 c. The fourth weighing is 1a vs. 1 b. If they balance the odd is is 1c and it is heavier. If they do not balance, then the odd coin is the heavier of 1a and 1b. Using this same methodology, the odd coin and its status may be determined no matter how each of the weighings turn out.
22. 1 point

9^(9-9)=1
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24. 1 point

## Lychrel

Code: #include <iostream> #define BUF_SIZE 100 using namespace std; void putInArray(int num, int* buf){ for(int i=0;i<BUF_SIZE;i++){ buf[i] = num % 10; num = num / 10; } } bool isPalindrom(int* buf){ int i=0, j=BUF_SIZE-1; while(buf[j]==0 && j>0){ j--; } while(i<j){ if(buf[i] != buf[j]){ return false; } i++; j--; } return true; } void applyIteration(int* buf){ int i=0, j=BUF_SIZE-1; while(buf[j]==0 && j>0){ j--; } while(i<=j){ int temp = buf[i] + buf[j]; buf[i++] = temp; buf[j--] = temp; } for(int i=0;i<BUF_SIZE-1;i++){ buf[i+1] += buf[i] / 10; buf[i] = buf[i] % 10; } } bool isLychrel(int* buf){ for(int i=1;i<50;i++){ applyIteration(buf); if(isPalindrom(buf)){ return false; } } return true; } int main() { int buf[BUF_SIZE]; for(int num=0;num<10000;num++){ putInArray(num,buf); if(isLychrel(buf)){ cout << num << " is Lychrel " << endl; } } }
25. 1 point

## Is it possible to give what we don't have?

Depends on what is meant by "have." [1] If have means "own," then yes. I can give someone something that I do not own. e.g. if I stole it. To give something, one only needs the ability to determine who controls it. If I control it, I can pass its control to someone else. So ... [2] If have means "possess the control of" then no. As stated, the paradox arises from the different antecedents of "with sorrow." Sorrow is the consequence of giving, not a possession before the act. But the language permits that interpretation by its form. Cute.
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