# Hello! PF users I'm new here

Hi!
I'm new here and seek some puzzles
for my mind.

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No! one!

All one will do is make you hungry. If you are hungry, you will need to eat. What is your favorite fish?

Welcome Mr.maniac!

Here is a puzzle

At the recent PF Festival, the 100 metres heats were closely monitored.

Each contestant had to run in two races so that the average place could be determined.

Only one runner finished in the same place in both races.

Alan was never last. Charlie always beat Darren. Brian had at least one first place. Alan finished third in at least one of the races. Both Darren and Charlie had a second place.

What were the two results?

Well, if you want a puzzle, why don't you try the Hardest Logical Puzzle Ever:

Three gods A, B, and C are called, in no particular order, True, False, and Random. True always speaks truly, False always speaks falsely, but whether Random speaks truly or falsely is a completely random matter. Your task is to determine the identities of A, B, and C by asking three yes-no questions; each question must be put to exactly one god. The gods understand English, but will answer all questions in their own language, in which the words for yes and no are da and ja, in some order. You do not know which word means which.

jtbell
Mentor
Speaking of fish and puzzles, a Google search for "fish puzzle" turned up the following:

http://web.stanford.edu/~laurik/fsmbook/examples/Einstein'sPuzzle.html

Let us assume that there are five houses of different colors next to each other on the same road. In each house lives a man of a different nationality. Every man has his favorite drink, his favorite brand of cigarettes, and keeps pets of a particular kind.

The Englishman lives in the red house.
The Swede keeps dogs.
The Dane drinks tea.
The green house is just to the left of the white one.
The owner of the green house drinks coffee.
The Pall Mall smoker keeps birds.
The owner of the yellow house smokes Dunhills.
The man in the center house drinks milk.
The Norwegian lives in the first house.
The Blend smoker has a neighbor who keeps cats.
The man who smokes Blue Masters drinks bier.
The man who keeps horses lives next to the Dunhill smoker.
The German smokes Prince.
The Norwegian lives next to the blue house.
The Blend smoker has a neighbor who drinks water.

The question to be answered is: Who keeps fish?
(And by the way, what's your favorite fish? )

Here is an extremele tough one:

The human race spread out to the stars, eventually terraforming and colonizing thousands of planets. On one planet, P3, they decided to perform an experiment in genetic engineering, attempting to develop a race of people who would always tell the truth. This, they thought, would turn the world into a perfect society - no one could get away with crimes or other deceitful activities. However, the experiment went awry and the engineered compulsion to tell the truth also acted as a compulsion to lie; these two happened randomly, with the person having no choice: he had to either lie or tell the truth as he was complelled to do at the moment. Thus no one could trust anyone because even if a person wanted to be honest he would lie randomly about half the time and never knew which ahead of time. So both the planet and the experiment were abandoned and the population was left to survive on its own.

Throughout thousands of generations evolution took its course and strict classes of periodic liars arose. Each person in class x would make a false statement exactly once every x times, with all of the intevening statements being true. Children were tested at an early age to determine their class, and each would be relegated to different roles in society. The classes were as follows:

Class 1: the Unbelievables: every statement was a lie. These formed the lowest level of society; they got no steady work and were often reduced to begging.
Class 2: the Two-Faced: every second statement was a lie, thus alternating between lies and truth. They performed the most undesirable work and often turned to crime.
Class 3: the Spinners: every third statement a lie. their motto: "Hey, 2 out of 3 ain't so bad!" They did standard blue-collar work.
Class 4: the Squares: every fourth statement a lie. They held the white-collar jobs.
Class 5: the Priests: every fifth statement a lie. The thought themselves superior and actually goverened the society.
Class 6 and above: various levels of High Priests. They made all of the rules and laws.

High Priests were rare. The higher the class the fewer the number of people in it. Occasionally an individual with an extremely high class number was born, usually double-digits, sometimes even over a hundred! These were called the Prophets. The held themselves aloof from society and often lived ascetic lives as hermits. They were revered as sages. Some of them formed secret religious societies, engaging in careful inbreeding, awaiting the birth of an "avatar", a person of class "infinity" who never ever told a lie. Skeptics would ask how could one ever tell if the alleged avatar was genuine; perhaps he just had a class number so high that he would not live long enough to tell his first lie!

This discriminatory class structure was hypocritcal, since actually anyone could gain another's trust by exposing himself as follows: a class 1 would simply say 2+2=5 twice in a row then the listener would know to believe the opposite of everything he says. And any higher class would simply say (at the proper time in his cycle) 2+2=4, 2+2=5, thus establishing himself as not class 1, and so his very next statement would be true. They could even use it to state their class number. And revering prophets as wise men was misguided. Telling the truth a lot did not mean a person was smart. He could be stupid, and when asked difficult questions would simply be compelled to say "I don't know the answer."

It should also be noted that not everyone belonged to the society. There were many left-overs from earlier times who were still compelled to lie randomly. These were called class zeroes and were totally banned from society; they lived in a primitive state in the wilds. They were looked upon as no better than animals and sometimes were even hunted for sport. Also, if any class zero attempted to enter the towns and villages they were immediately killed.

Eventually the planet was rediscovered by the spacefaring civilizations. After the initial language difficulties were surmounted, the natives saw that the spacemen seemed to always tell the truth and were thought to be high-class prophets. But eventually they were caught telling occasional lies, and not periodically. Many natives considered them to be class zeroes and wanted them to leave the planet. No one actually wanted to try killing them since they were obviously much technologically superior, and thus too dangerous. But others realized they lied voluntarily, not compulsively or at random, and the High Priests designated them as "classless aliens" and were to be tolerated but not trusted.

During the hundreds of years following there was extensive trade and interaction with the aliens, and the inevitable interbreeding, so the native population became more and more able to lie voluntarily and eventually became indistinguishable form the aliens, as far as lying was concerned. The class system disappeared and since no one could any longer trust anyone else, and the society collapsed, reverting to barbarism. By this time the class zeroes had all been exterminated and eventually the population was subjugated by the space-faring civilizations and used as slave-labor.

But Anyway...

Now it so happens that among the numerous secret societies on P3 there is one group that calls themselves the PsychoMaths. They create all sorts of numerical and logical puzzles and challenge one-another at their meetings. On of their favorite pastimes is playing the game of Number Match. A referee chooses 5 players, no two of which are of the same class, who play the game for 10 rounds. During each round each player secretly chooses and writes down a number from 1 to 5 and gives it to the referee. Once all numbers are in the referee exposes them all and delcares the winner, who is determined by the Match Rule: Any player whose chosen number is the same as that of any other player(s) is said to be matched; all other players are unmatched. The winner is the unmatched player having the highest number, and he scores points equal to his number; no other players score that round. If all players are matched no one wins that round and no one scores.
(Examples: if the numbers are 4,5,5,3,4 then only 3 is unmatched and wins. If the numbers are 5,2,5,4,3 then 4, 3, 2 are unmatched and 4 wins.) After the 10 rounds are over the referee calculates the total scores for each player and then the winner is determined from these 5 scores by using the Match Rule again: the player having the highest unmatched total score wins the game.

The game is played in secret and after the game is over each of the 5 players in turn makes 6 statements about the game which the referee carefully records on paper, in the exact order stated. During this recording session absolutely no other statements are made by the players. For the written statements the players are assigned letters A,B,C,D,E in order to remain anonymous. Then the statements are presented to the full membership of the society as a puzzle, and they attempt to deduce who was the winner.

Below are the statements of a recent game, listed in exact order:

A1: I won the second round.
A2: I won the last 2 rounds with equal scores.
A3: No one's total score was higher than mine.
A4: I never won with 5.
A5: I won the fifth round.
A6: I did not win the game.

B1: Three of the players never chose 4.
B2: I won the third round.
B3: My total score was lower than any of the others.
B4: I chose 2 in every round.
B5: I won the seventh round.
B6: I won the sixth round.

C1: I did not win the eighth round.
C2: My total score was 14.
C3: I chose 4 in the first round.
C4: I won the first two rounds.
C5: I did not win the sixth round.
C6: I chose a different number in each round I won.

D1: No one won 2 consecutive rounds.
D2: I chose 4 in every round.
D3: I won the first round.
D4: No one won more than 3 rounds.
D5: I won 2 of the first three rounds.
D6: I lost every even-numbered round.

E1: I did not win the first round.
E2: No one ever chose less than 3.
E3: No one ever won with 3.
E4: I won the sixth and seventh rounds.
E5: I won the seventh and eighth rounds.
E6: I did not win the third round.

Can you determine the winner?

Remember: each player is of a different class. All 5 total scores can be determined, but not the exact number choices of the losing players of each round.

Also note that when a player makes his first statement you do not know at what point in his lie-cycle he is at, so his first statement could be true or false depending on the last time he lied as well as his class.

Yet another one:

You have a pile of N stones. You do the following: you take a pile and separate it into two smaller piles, multiply the numbers of stones in these two piles, and write this number on the blackboard. You do that until there is N piles with only one stone in each. Then you take a sum of all numbers written on the board. What result can you get?

Maybe an example will be instructive:
STEP 1: We divide it in two piles with 70 and 30 stones, thus we write 70*30=2100 on the board.
STEP 2: We divide the pile with 70 into two piles with 2 and 68, thus we write 2*68=136 on the board.
STEP 3: We divide the pile with 2 rocks into two pile with 1 rock each, thus we write 1*1=1 on the board
STEP 4: We divide the pile with 30 rocks into two piles with 15 rocks each, thus we write 15*15=225 on the board.
STEP 5: ......

As you can see, it doesn't matter which pile you divide into two piles and it doesn't matter into what numbers you divide the pile. Still the eventual sum of all the numbers on the board will be equal!!

This is one of my favorites:

Ants on a stick may only march left or right, all with the same constant speed. They never stop, short of falling off the stick. When two ants bump into each other they bounce and reverse their directions.

Assume 25 ants were randomly dropped on a 1 meter stick and move with constant speed of 1 m/sec. 25 ants create real commotion marching this way and that way, bouncing off each other, and occasionally falling off the stick.

Is this certain that eventually all the ants will fall off the stick?
If so, in the worst case scenario, how long it may take for the stick to become ant free?

Borek
Mentor
You may also try proving that the real part of every non-trivial zero of the

$$\zeta(s) = \frac{1}{\Gamma(s)} \int_{0}^{\infty} \frac{x ^ {s-1}}{e ^ x - 1} \mathrm{d}x$$

function is 1/2.

DataGG
Gold Member
And he'll never join PF again...

jtbell
Mentor
I guess this is our new "puzzle-slapping" initiation ritual. :uhh:

I guess this is our new "puzzle-slapping" initiation ritual. :uhh:
We should request everybody wanted to join to solve one of the above puzzles as anti-spam measure

WannabeNewton
Fighting spam with spam: didn't Gandhi have something against that?

Welcome Mr.maniac!

Here is a puzzle

At the recent PF Festival, the 100 metres heats were closely monitored.

Each contestant had to run in two races so that the average place could be determined.

Only one runner finished in the same place in both races.

Alan was never last. Charlie always beat Darren. Brian had at least one first place. Alan finished third in at least one of the races. Both Darren and Charlie had a second place.

What were the two results?
As per the precedent set in the Enjoyable Enigmas thread I am permitted to ask clarifying questions.

You describe the races as "heats". By that you mean: "a less important race or competition in which it is decided who will compete in the final event," correct? 4 contestants are named, so I assume that is the total number of participants. It is asserted that each ran two races, therefore the total number of "heats" was 2, and each of the 2 heats had the same 4 contestants, correct?

Greg's
n=4
A!=4 (1,2)
C<D
:.C!=4 (1,2)

B=1(1&/2)

1......2
1 C . 1 B
2 D . 2 C
3 A . 3 A
4 B . 4 D

or in English- race a) 1 Charlie 2 Darren 3 Alan 4 Brian
race b) 1 Brian 2 Charlie 3 Alan 4 Darren
?

Fighting spam with spam: didn't Gandhi have something against that?
It is better to spam, if there is spam in our hearts, than to put on the cloak of non-spamming to cover impotence.

Last edited:
Hey guys, new to the forum.

Just wanted to say I really enjoyed the puzzles and can tell that there is a good bunch of smarts around, look forward to discussions with you involved.

P.S. any more puzzles? ;)

Schieder
Welcome Mr.maniac!

Here is a puzzle

At the recent PF Festival, the 100 metres heats were closely monitored.

Each contestant had to run in two races so that the average place could be determined.

Only one runner finished in the same place in both races.

Alan was never last. Charlie always beat Darren. Brian had at least one first place. Alan finished third in at least one of the races. Both Darren and Charlie had a second place.

What were the two results?
Heat1: 1st Charlie 2nd Darren 3rd Alan 4th Brian
Heat2: 1st Brian 2nd Charlie 3rd Alan 4th Darren

Ryan_m_b
Staff Emeritus
Welcome Mr.maniac!

Here is a puzzle

At the recent PF Festival, the 100 metres heats were closely monitored.

Each contestant had to run in two races so that the average place could be determined.

Only one runner finished in the same place in both races.

Alan was never last. Charlie always beat Darren. Brian had at least one first place. Alan finished third in at least one of the races. Both Darren and Charlie had a second place.

What were the two results?
1st race: Charlie, Darren, Alan, Brian
2nd race: Brian, Charlie, Alan, Darren

Taking the average: Charlie, Brian, then Alan and Darren are joint.

But PF would never have such a shoddily designed tournament! Everyone knows that it's three repeats minimum :tongue2:

Welcome Mr.maniac!

Here is a puzzle

At the recent PF Festival, the 100 metres heats were closely monitored.

Each contestant had to run in two races so that the average place could be determined.

Only one runner finished in the same place in both races.

Alan was never last. Charlie always beat Darren. Brian had at least one first place. Alan finished third in at least one of the races. Both Darren and Charlie had a second place.

What were the two results?
Alan I guess

It is better to spam, if there is spam in our hearts, than to put on the cloak of non-spamming to cover impotence.
You're a character of sonic Dr.Eggman
just you changed your name a bit

I'm a 7th kid dont sum me up with calculus

I'm a 7th kid dont sum me up with calculus
But dont underestimate me with circles
Archimedes

All one will do is make you hungry. If you are hungry, you will need to eat. What is your favorite fish?
Paedocypris progenetica