BrainDen.com - New Puzzles & Riddles

Outwit or die

Mon, 06 Jul 2009 13:07:59 +0000

A dog is in the center of a round swimming pool (radius 100 meters). A tiger, who can't swim, is on the edge of the swimming pool and tries to catch the dog. What is the maximum ratio of the tiger's running speed and the dog's swimming speed such that the dog can swim ashore without being caught by the tiger? What strategy (i.e. swimming route) should the dog use?

Prisoners on a death row again

Mon, 06 Jul 2009 06:32:43 +0000

Twenty prisoners are on a death row and are allowed a chance to live through a game. The game is as follows. Each prisoner, as they enter the room on the day of the game, is given a hat with a random number ranging from 1 to 20. The numbers of the hats are independent of one another. The prisoners then stand in a circle, and each one can see what the other nineteen have on their hat, but not his own hat.

After the prisoners stand in a circle, the prisoners are allowed 3 minutes to think of a guess for the hat they are wearing. At any time that a prisoner is ready with his answer, he can raise his hand to indicate that he is ready. The other 19 prisoners, being in the same room, can see whenever someone raises his hand. Assume the prisoners can not communicate with each other in any other ways such as raising his hand with different number of fingers extended, raise it with different speed, make his fist into a prearranged shape, etc. The only information available to each prisoner is the other 19 numbers, and the order in which his fellow prisoners indicate they are ready.

After 3 minutes, or after all 20 indicate that they are ready, whichever is sooner, each prisoner is required to write his guess for his hat number without being seen by the other 19. All prisoners write down their guess simultaneously. If all 20 guesses are correct, the prisoners win and all are released. If 1 or more is incorrect, all 20 will die.

With optimal strategy, what is the chance of winning for the prisoners? Describe the strategy.

Hardly Belligerent

Sun, 05 Jul 2009 21:34:05 +0000

Hardly belligerent, by any means
But just one step away from fighting mean
It's a thing that can be seen
But not in it's extreme
(Whose birthplace is the sun
With effects far from fun)
Nature's tooth and claw is on the other side
Mirroring the answer over which I preside
If you still need a clue, here's what I'll do:
I'll give you two-combining's up to you
A glass, a container
To permit, or enable
That's all I have to say so
Good luck with this riddle

Sphere Chasing, Cube Punching and Hide-and-go-Seek-Tag

Sun, 05 Jul 2009 21:17:46 +0000

A collection of random problems I've come up with over the past few days... [please use spoilers when answering!]

(1) A large sphere of radius 'r' is rolling around the interior of a massive cube-shaped room, chasing around a smaller sphere. The room's volume is thousands of times bigger than the larger sphere and completely empty (other than the spheres). The smaller sphere's radius is some constant multiplied by 'r'. The smaller sphere is rolling away from the larger sphere, trying to escape... it quickly realizes that the only possible escape is to wait it out against the edge or in the corner.
(1a) What is this constant's upper limit if the smaller sphere can fit against the edge of the floor and a wall and not touch the larger sphere?
(1b) What is this constant's upper limit if the smaller sphere can fit snugly in the corner of the room (ie, the floor and two walls) and not touch the larger sphere?

(2) You have a 10 by 10 by 10 cube, made of 1000 unit cubes. You also have a "punching device", which can be aimed at a specific surface unit square and pointed perpindicular to that surface square. This "punches out" and gets rid of all of the cubes in that column. If this is hard to understand, I can elaborate further. The question is, what is the maximum number of "punches" you can use to completely eliminate all of the cube?

(3) You are playing hide-and-go-seek-tag with a friend (problems of this type also translate into scenarios where two separated parties are looking to meet up and are simultaneously moving around). You and your friend are in an area that can be described as a circle with a circumference of 100. You are at one point on the circle, your friend is somewhere else. Assume that if someone is going in one direction at a constant speed, they won't change directions. Also, your speed is 'v', your friend's speed is 'w', and v>w>0. All of this applies for both sub-problems.
(3a) It's a tossup whether your friend is going to stay put, move counterclockwise or move clockwise. Because you don't know which of those three options your friend will choose, and the game has to end sometime, you HAVE to move, either clockwise or counterclockwise (you intend to flip a coin to choose which way to go). What is the average time it will take for you to catch your friend?
(3b) In this scenario, you know that your friend is NOT going to stay put... so you have to choose, between moving (either counterclockwise or clockwise) of course, or staying put and waiting. What is the average time it will take for you and your friend to meet up in both cases (ie, with you moving too or with you staying put)? So, what should you do - stay put or move? And what is your answer to that if v=5 and w=3? For what set of speeds (v,w) does it not matter whether you go or stay (ie, both options have the same avg time) and what does this have to do with the golden ratio?

~~~

thanks and good luck

Mirror image....maybe

Sun, 05 Jul 2009 18:17:30 +0000

A word of five; it takes you away
To places you can never really be
Bliss or torture, you decide
You might just want to stay and abide

Horizontal flip; a tool, a part
Gives you sweet images, but grotesque at heart
A plural, maybe rural; taking out....so true
Could be good, could be bad; it's up to you.

A Woman Scorned

Sun, 05 Jul 2009 17:19:01 +0000

1. Attack lost land before the arrangement.

2. Nothing left to recycle is unspoiled.

3. Gravel goes back and forth.

4. Finish with good left hook.

5. Burn a lady which bewitches.

6. Settle so others without rupees are left to remain.

7. Undermining the morale of the planet fosters a core upheaval.

8. Break each holy man's chest.

9. After a mile out at sea Theodore was tied up.

10. Go back for second ACORN result.

In no particular order, the number of letters of these answers are as follows: 3, 4, 5, 5, 6, 6, 6, 6, 6 and 7

Bonus: One has 5:55 the second 6:52 third or fourth a 9:10.
(Probably can only be completed once the others are solved...unless you are extremely clever!)

helium balloon trick?

Sun, 05 Jul 2009 14:43:05 +0000

ok I saw this on a different site (forget where or what I was doing there) so after an extensive search, I did not find it here...there was quite a debate over the answer on the site I saw it on, so I thought I'd post it here to see what some of you guys think.

Here's the set up: You're driving down the road, and have a balloon filled with helium tied to the floor. If you were to take a sharp right turn, what way will the balloon lean? Why?

What's the size of the cycle?

Sun, 05 Jul 2009 00:25:01 +0000

We define a sequence of numbers, all less than 1,000,000,000, in
the following way:

We start with the number 123,456,789. If our current number
is N, the next number in the series is

((732,891,011 * floor(N/60)) + 345,678,911) modulo 1,000,000,000

where "floor(x)" is the largest integer less than or equal to x
(in other words, the integer part of x), and
"y modulo 1,000,000,000" is simply the 9 least significant digits
of y (in other words, the remainder after you divide y by
1,000,000,000).

Now, because the numbers in this sequence are all less than
1,000,000,000 , the sequence must eventually fall into a repeating
cycle of numbers. What is the length of this cycle?

Feel free to write a program to compute this. Or even give
a description of the algorithm such a program should use. Try
not to use any large arrays in the program.

Good bye

Sat, 04 Jul 2009 16:08:21 +0000

The Prima Donna
Sings her piece
Giving her a
Sweet release

From life and pain
And being abused
Her feelings wasted
Burnt up and used

She sings her song
So sad and true
A once bright spark
Turned cold and blue

She sheds a tear
And nothing more
Nearing the end
Sinks to the floor

Finally she sings
Her last note
And that, my friends
Is all she wrote

the rules of atomic war

Sat, 04 Jul 2009 15:42:02 +0000

two sides, America and Russia, are facing off in a deadly game.
america has the technological advantage, they have more missile silos, a total of 12.
however america only has 10 primary cities.
russia has the people advantage, they have 14 primary cities, but only 10 missile silos.
both sides want to disable each other's missile silos while causing maximum damage to the population, in order to win. both sides have an agreement that they will only fire 1/2 of their missile silos every "round" until one side has won or the other. there two ways to win, are either destroy all missile silos or destroy all the primary cities.
as an example game, in the first round, russia uses 2 missiles on the missile silos, and 3 missiles on the primary cities; while america uses 4 missiles on the missile silos and 2 missiles on the primary cities.
russia now has 6 missile silos and 12 primary cities while america has 10 missile silos and 7 primary cities.
in round 2, russia uses all 3 missiles on the primary cities, and america splits its attack again , using 2 missiles on the missile silos, and 3 missiles on the primary cities.
russia now has 4 missile silos and 9 primary cities, while america has 10 missile silos and 4 primary cities.
in the final round, russia trying for the knock out uses both missiles on the primary cities. america splits its attack and ends the game, using 4 missiles on the missile silos and 1 missile on the primary cities.
final result america wins, with 2 primary cities left and 10 missile silos while russia has 0 missile silos and 8 primary cities.

now, assume both sides use a random number generator to determine how many missiles they'll use on cities and on missile silos. what is russia's chances of winning?
(if a player has an odd number of missile silos he'll round up when firing.)

BOOKENDS

Sat, 04 Jul 2009 04:37:23 +0000

?ENTETTFFSSENT?

Lemony

Thu, 02 Jul 2009 17:39:30 +0000

So unfortunate, what a shame.
But unlucky is also a name.
Without luck or good things,
Misery and sadness; what I bring.

Lemony had a series of events,
Mostly me, is what they meant.
There is luck all around, indeed.
Without, is the answer I need.

Burden

Thu, 02 Jul 2009 15:47:08 +0000

Too heavy, we�re going down.
Come back later, it may be found.
Not stable, we need to act
Lighten up; for more come back.

Discarding opposite of the bads
It�s an emergency, use all hands.
Burden gone, keeping us high.
Staying up, that�s all. It�s why.

hurt

Thu, 02 Jul 2009 14:29:31 +0000

Washing dishes can get you hurt,
But in my presence, the blood won't squirt.
In went the hand to the sink full of suds.
Out it came, covered in blood.
Never a dull moment when I am here.
Two words you'll find, when the answer is clear.

excel team layout

Thu, 02 Jul 2009 14:08:10 +0000

Here is the teaser:

On an excel spreadsheet, how do I lay out a card playing tournament with the following criteria?

1) There will be 8 teams

2) Two persons to each team

3) Each team must play all other teams, but cannot play the same team more than once.

Cheers!

Now I see you; now I don't

Thu, 02 Jul 2009 13:09:52 +0000

Sitting quietly; there, I see
A sudden fear siezes me
Am I sure; is it real?
Maybe my head's in a whirl

I go; and i'm horrified...
My fears have been clarified
It was a nightmare; turned real
Oh, my head hurts; I need to heal...

Spoiler for important...:

The winner looses money

Thu, 02 Jul 2009 12:19:54 +0000

100 people ( Player 1, Player 2, ... Player 100) are playing a game.

In the first round Player 1 wins.
In the second round Player 2 wins
In the third round Player 3 wins and so on till 100
so in total 100 rounds of the game are played.

If a person wins a round he has to give some money to the other 99 players. The winner must double the money of each of the other players (that they had before the start of the round).

Example; if when Player 5 won the 5th round, he doubled the money all other players at the start of round 5. In the 6th round, player 6 doubled the money other players had at the start of round 6 (same as end of round 5 after player 5 had distributed the money to other players).

At last after the 100 th player wins the amount of money which everone has is same and is "X"

Questions:
1) Which player(s) ended up richest? (i.e. richer meaning that the player had more money at the end of the game than he had at the beginning of the game)
2) Which player(s) lost the most money?

For math lovers:
3) How much money did the 63rd player had in beginning of the game in terms of "X"?

primetime POWs

Thu, 02 Jul 2009 09:57:46 +0000

1. Four vertical supports, a lid, and a human engine inside
2. See? Snake eyes!
3. And, shortened, see me twist
4. One speaking softly to those who have passed
5. 1,2 buckle my shoe; 3,4 shut the door, etc...
6. Bumbershoot left by the house opposite the upturned boat
7. Sneezing, coughing, sniffling, aching satchel
8. The grown boys have height catalogued, but not doubled, together
9. Internal support structure?
10. The outside edge
11. Suddenly, completely and utterly gone
12. Higher functions of lowly persons
13. Just right, in other words, to Goldilocks
14. Two baker's worth, after the baker's have theirs
15. Rules and Regulations

*Extra Credit*
1. The area of time and space between the light and darkness
2. The nether reaches ends

I won't be here to help you guys today, but I'm almost certain these will be solved before noon! I'll be back tonight to check on progress. These are all current primetime TV shows, and remember they are POWs, so what's written doesn't necessarily have anything to do with the show its describing, just the name of the show.

good luck, and happy riddling!

(P.S. Feedback, comments, complaints are always welcome. I'd love to improve my game!)

Chess_Vixen

Doctor Eye

Wed, 01 Jul 2009 22:43:04 +0000

This is the story of Doctor Eye
Every patient he had he did not like
His specialty sometimes made people cry
But normally it just made them fly

Brain dead, hand to head,
Losing calm, facepalm.
Aging spit, no good to hit,
Need repair, or a spare

Spoiler for first pointer:

Something Wicked This Way Comes

Wed, 01 Jul 2009 22:38:46 +0000

Rise from the ashes,
Up from the ground,
Gather your brothers,
And start the round.

Follow the Creator,
And hunt down the prey,
Be careful of weapons,
They will blow you away.

Spoiler for Hint...:

A tragedy

Wed, 01 Jul 2009 22:20:12 +0000

You didn't mean it, or maybe you did,
but they still deserved a chance to live!
You made it so their voice wasn't heard,
now they can't say a single word.
No one can ever hear their voice,
all because of your dumb choice.
Someone needs to stand up for them,
so this never happens again.
But they're in luck, I'm spreading the word,
mabey their voice will finally be heard.

Philosophical Design

Wed, 01 Jul 2009 21:53:21 +0000

Two words together describe this to tame
In a strange way my meaning is just the same
Whether read word by word
Although it sounds quite absurd
All allude to my circuitous fame.

You don't want to meet me accidentally
Then draw near, be alert most mentally
Can go this way or that
Depends where you're at
So surely you can approximate my identity.

Serum

Wed, 01 Jul 2009 21:34:19 +0000

Deceiving? Oh yes, my intent.
False impression? What I meant.
Lookin� good, and that�s a fact
So small, nothing; but not black.

True or False, or Multiple Choice.
One of those, the answer voiced.
Deliberate, a statement made.
More and more. Spiders don�t fade.

Hunger Games

Wed, 01 Jul 2009 20:32:24 +0000

I�m so hungry, can�t seem to get full.
I eat and eat, but it�s always null.
It is rapacious, this desire in me.
To go for the kill, get more than I need.
Getting fatter or not, it�s all the same.

Gaining and taking, never giving it back.
Ravenous, always, after a meal or snack.
Eating all the time, but always want more.
Even needing more than deserved, for sure.
Daring to compete in this selfish game.

Never ends well, this inordinate want.
I can�t stop eating, whether I want to or not.
Let�s face it though, I always want to indulge.
Same as before, I just like the bulge.
Wanting, eating, needing. I feel no shame.

What I hate about you

Wed, 01 Jul 2009 19:00:01 +0000

You give me a glare that hurts so bad,
you know just what to say to make me mad.
What is it that I hate most about you?
What makes me despise you, in all that I do?
Is it that fake smile, your hand on your hip?
Your painted on face, or that plumped up lip?
Well I don't care,
You can only stare.
But I know the battle's not won,
You'll get me back with your wicked tongue.
But it's not just you, it's the rest of your clique.
Who�s the cutest? Boys-take your pick.
But I'd take it slow, you know you can't take her,
when it comes to dating she's a real heart breaker.
You can call me a dork, a geek or a nerd,
But what you don't realize is your words can hurt.
Or maybe you do, and it just brings you joy,
to mess with the feelings of each girl and boy.
You torture all who go to this school,
and everyone knows that's just not cool.
For there's only one thing that hurts more than a punch,
and it's that nasty rumor you spread at lunch.

How is it possible?

Wed, 01 Jul 2009 17:17:31 +0000

If 182 + 235 were equal to 427, what would 21 times 17 be?
Why?

Tough Math/Logic

Wed, 01 Jul 2009 12:55:16 +0000

Question 1
(x-a)(x-b)(x-c),,,(x-z)=
Solve for

Question 2
You have a chessboard, on which the two opposing diagonal corner squares have been removed. You have an infinite number of domino's, each of which cover exactly two squares on the chessboard. Without any domino overlapping another, and no domino hanging over an edge (So each domino must cover two squares) can you completely cover the chessboard with domino's?

Question 3
You have 10 trees in pots. Is it possible to plant the trees in five rows of four trees?

circle on a chess board

Wed, 01 Jul 2009 11:29:25 +0000

A chessboard has squares that are two inches on the side. What is the radius of the largest circle that can be drawn on the board in such a way that the circle's circumference is entirely on black squares?

Catching a Pirate Ship

Wed, 01 Jul 2009 08:35:06 +0000

I searched for this really hard given my last failure and didn't find it posted hear. It is an elegant pursuit puzzle.

You're on a government ship, looking for a pirate ship. You know that the pirate ship travels at a constant speed, and you know what that speed is. Your ship can travel twice as fast as the pirate ship. Moreover, you know that the pirate ship travels along a straight line, but you don't know what that line is. It's very foggy, so foggy that you see nothing. But then! All of a sudden, and for just an instant, the fog clears enough to let you determine the exact position of the pirate ship. Then, the fog closes in again and you remain (forever) in the thick fog. Although you were able to determine the position of the pirate ship during that fog-free moment, you were not able to determine its direction. How will you navigate your government ship so that you are sure to capture the pirate ship?

Implants

Tue, 30 Jun 2009 22:11:17 +0000

What color? Oh, not fake.
I�m all natural, it�s innate.
It�s God given, I know.
Easy work, does it show?

Small to big, that�s how
I�ve looked for a while now.
Bursts here, lighten up.
Lava, no? Close enough.

Breakfast

Tue, 30 Jun 2009 21:05:13 +0000

Outside or in, run and enjoy.
Out instead, no room for the boy.
Not nice? Then sugarcoat it.
Like 123, but not. End the British bit.

Now something new, not done
By me before. I hope it�s fun.
Break it up, then answer it all.
Add it together, and it's solved.

Jazzy!

Tue, 30 Jun 2009 20:50:54 +0000

Vaughan, do no fun! Just match Coltrane.
Criteria: improvisation sounds new.
The answer, I says, comes afternoon.
Do no jazz sane!

Are you crazy Bob?!

Tue, 30 Jun 2009 20:46:36 +0000

Bob is walking down the street in the middle of the night, and he starts to get the feeling of being watched. Not just being watched-being followed! He starts to get scared, but then the glowing eyes give it away. It has razor sharp teeth and claws to match, and I really don't think you'd want to get it angry. It's hearing is better than most dogs, and it can see you even if it's pitch black. it can hunt down and kill more than a hundred different species of animals, and worst of all, it's a world conqueror. It has already taken over six of the seven continents! But surprisingly, Bob isn't scared. In fact, he picks it up!!! Is he crazy, or does he know something I haven't told you?

Casting Shadows

Tue, 30 Jun 2009 20:38:36 +0000

Splitting time between heaven and earth.
Valueable lessons of telling worth.

A long time ago they were unsurmounted.
Scored before penmanship even was counted.

Codified simply, five fingers, two hands.
The closer to beam, increasing demands.

Start once again with this knowing jab.
A custom to stick, not intending to stab.

The truth simply hidden, revealed in this frame.
Now tell me please, of this subject, its name.

A strange interpretation for beauty

Tue, 30 Jun 2009 20:10:24 +0000

Everyone knows who I am,
I cover all but frozen lands.
Not two, not four, but six legs,
We�ve changed so much since we were eggs.
I was a small, squirmy thing,
But I now take pride in all four wings.
I have fur, feathers, and even scales!
I�ll eat mold and dung, if all else fails.
Yet I still stand for love and beauty,
Some cultures even worship me.

I have no idea how easy or hard this is, but I still hope you like it.

Good company, i feel....

Tue, 30 Jun 2009 18:47:37 +0000

Why are you standing there; look
I'm definitely a word you've seen in the book
Emphasize, why?.....reason it out
Don't yell at me; it's not what you thought
Wanna play pool? i detest math,
Put them together; and that is that...

like most of my riddles, please find the word and the relation with the title

P.S: It's not movies this time

Set Sail

Tue, 30 Jun 2009 18:21:20 +0000

They had words. Upset kind.
Arrangement here, side by side.
Some have said delicate, it�s true.
Grainy texture. Not for me, you?

Soda Leader

Tue, 30 Jun 2009 17:58:06 +0000

Ask anyone, I�ve walked the moon.
No one knows; black, white? Too soon?
Coke, Pepsi, Sprite. Or really just pop.
I�m the king, whether you�re thrilled or not.

Spoiler for Disclaimer:

Hiding in Plain Sight

Tue, 30 Jun 2009 17:16:13 +0000

Hello everybody! First in a while. We shall see how it goes.

I can be tricky to those, who are unfamiliar
ESL students, are initially left bewildered
Those who are well versed, participants in a bee
Have no problems, finding me

I have a home in Arkansas, and Illinois, too
Also exotic lands, within an island, it's true
When you throw out your trash, I am inside your debris
In the aisles you walk down, look to find me

House Party

Tue, 30 Jun 2009 17:11:10 +0000

Oh it is so annoying, I hate it the most.
Not going to parties, they only host.
It�s nice to go, and so fun to interact.
But other�s host too. And that is a fact.

Stay at their party, thinking they�re the best.
Having everyone come. They ignore the rest.
In and out, but rarely showing their face.
Only to accept compliments on the place.

Others host parties, I know this very well.
I�ve been to quite a few, so fun, can�t you tell?
Parties are great, and they are made to hop.
Go to them all. Not just yours, stopped.