Illustrated Riddles from Open University

Some fun illustrated riddles and insight on problem-solving.

http://www.openuniversity.edu/news/news/riddle-me-this

The Cosmic Number

four is cosmic

4 is cosmic.

1 is 3, 3 is 5, 5 is 4, and 4 is cosmic.
8 is 5, 5 is 4, and 4 is cosmic.
2 is 3, 3 is 5, 5 is 4, and 4 is cosmic.
15 is 7, 7 is 5, 5 is 4, and 4 is cosmic
9 is 4 and 4 is cosmic.
18 is 8, 8 is 5, 5 is 4, and 4 is cosmic.
17 is 9, 9 is 4, and 4 is cosmic. 
100 is 10, 10 is 3, 3 is 5, 5 is 4, and 4 is cosmic.

If you think you recognize the pattern, submit an example.  If you need more examples, I can give you more.

Running Out of Riddles

Well I thought I could make it a whole year providing a new riddle every week, but it appears I am almost out.  I will continue posting puzzles as I find them, but I can't guarantee a weekly riddle any more at this point.  For now, an old one my dad once told me:

What did the left eye say to the right eye?

The Hateful Neighbors

The Boggis, Bunce, and Bean families were once united in their pursuit of a common enemy, but have since developed a bitter and irreconcilable hatred for one another.  Each family lives in its own house in its own part of town, and all is well and good, so long as members of different families don't cross paths - if they do, they will start brawling until the poor sheriff has to come out and break them up.  They are very civil indoors, however. 

Each family needs to be able to access the post office, the general store, and the sheriff's office without encountering members of other families.

So the sheriff has come up with a great plan; draw up plans for each family to have its own three paths, traveling from each home to a each of the three municipal buildings.  In this way, for example, the Boggis family has three paths, where each path leads from its front door to the front doors of the post office, general store, and sheriff's office.  Can he do this without letting the paths cross, and without digging any tunnels or building any bridges - in other words, working in a two-dimensional plane?

1000 Bottles of Wine

Borrowed from folj.com. 
You are the ruler of a medieval empire and you are about to have a celebration tomorrow. The celebration is the most important party you have ever hosted. You've got 1000 bottles of wine you were planning to open for the celebration, but you find out that one of them is poisoned.
The poison exhibits no symptoms until death. Death occurs within ten to twenty hours after consuming even the minutest amount of poison.

You have over a thousand paid caterers to help with the testing and just under 24 hours to determine which single bottle is poisoned.

You have a handful of prisoners about to be executed, and it would mar your celebration to have anyone else killed.

What is the smallest number of prisoners you must have to drink from the bottles to be absolutely sure to find the poisoned bottle within 24 hours?

SEND MORE MONEY

One time in college I emailed my dad asking for money and he said I could have some if I solved the following equation:

   SEND
+MORE
_______
MONEY

Each letter represents its own digit (0-9) and multiple occurrences of the same letter represent the same digit (eg if one of the E's represents a 3, they all do).

A Boat in a Tank

Imagine you are in a small rowboat floating in a swimming pool.  There's a big rock in the boat and you drop it overboard. Does the water level rise or fall?  Why?

The Magic Square

This is one I come back to when I'm bored and all I have is pen and paper.  I also read in a biography of Benjamin Franklin that he used to do this when he was stuck in boring meetings.  Construct a 3x3 grid of numbers, using numbers 1 through 9, and arrange the numbers in the square such that every row, column, and diagonal (diagonals through the center) adds up to 15. 


Too easy?  Now construct a 4x4 grid made out of numbers 1 through 16, such that every row, column, and diagonal adds up to 34.  This one is killing me because I figured it out once, but can't seem to rediscover the solution.  There are ways to do this for grids 5x5, 6x6, and up, though they no doubt get very difficult.

No Riddle This Week

I can't think of any and I'm too busy with work, sorry everybody. 

4=5

The other day, someone in our creative services department tried convincing me that 4=5.  He offered a convincing proof, which is displayed below.  But what is wrong with it? 

Pirates, Part 2

Again, taken from folj.com. 

The five pirates mentioned previously are joined by a sixth, then plunder a ship with only one gold coin.


After venting some of their frustration by killing all on board the ship, they now need to divvy up the one coin. They are so angry, they now value in priority order:

1. Their lives
2. Getting money
3. Seeing other pirates die.


So if given the choice between two outcomes, in which they get the same amount of money, they'd choose the outcome where they get to see more of the other pirates die.


How can the captain save his skin?

The Blind Date Bachelor

(Modified from a puzzle about a sultan and his harem I heard from Jon Huang.) The Blind Date Bachelor is the newest dating show, in which where there is 1 bachelor and 4 contestants trying to win his heart. He will meet each contestant for the first time on a blind date. At the end of the date, he must choose whether to marry her or never see her again. If he marries her, the game is over. If he rejects her, he is set up on a date with the next contestant and repeats the process. If he rejects the first 3, he marries the last one automatically. He is able to compare and rank contestants that he has already met, but will not know for sure who he likes best until he has met them all. It's very important that he marry the best one, or he will spend the rest of his life wondering what could have been. What strategy will maximize his chances of finding the best mate-for-life?

3 Bonus Questions: What is the probability of winning using the best strategy?  What if there are 5 contestants, not 4?  And finally, what if there are n contestants? 

Pirates

I've seen this one before and haven't solved it.  Go ahead and comment answers in the blog, but not on Buzz or else  people will see them.  I quote this one from folj.com, but I've seen it before in other places as well. 

Five pirates have obtained 100 gold coins and have to divide up the loot. The pirates are all extremely intelligent, treacherous and selfish (especially the captain).

The captain always proposes a distribution of the loot. All pirates vote on the proposal, and if half the crew or more go "Aye", the loot is divided as proposed, as no pirate would be willing to take on the captain without superior force on their side.
If the captain fails to obtain support of at least half his crew (which includes himself), he faces a mutiny, and all pirates will turn against him and make him walk the plank. The pirates start over again with the next senior pirate as captain.

What is the maximum number of coins the captain can keep without risking his life?

Dots and Lines

This is a very old one, and many of you may have seen it before.  I try to avoid posting puzzles with outside-the-box solutions, but I made an exception for this one.  Using 4 straight, connected lines, connect all 9 dots.

Heads and Tails

This is borrowed from folj.com and I don't know the solution.  Submit ideas in the comments section - maybe you'll get it before I do. 

There are twenty coins sitting on the table, ten are currently heads and ten are currently tails. You are sitting at the table with a blindfold and gloves on. You are able to feel where the coins are, but are unable to see or feel if they are heads or tails. You must create two sets of coins. Each set must have the same number of heads and tails as the other group. You can only move or flip the coins, you are unable to determine their current state. How do you create two even groups of coins with the same number of heads and tails in each group?  [Note: I assume you need a guaranteed method of getting even groups, rather than method that will likely work.]

The Lantern and the Bridge

A small family is being pursued by an unknown enemy in the middle of a dark, dark night.  It comes to a deep chasm spanned by a narrow bridge. 

The family is composed of a father, mother, grandfather, and child.  The father is athletic and can cross the bridge in 1 minute; the mother can cross in 2 minutes; the child can cross in 5 minutes; and the grandfather, the slowest, takes 10 minutes to cross.  They have a lantern with them. 

Since it's pitch dark, the bridge can't be crossed without the lantern.  The bridge is so narrow that only two can cross at a time, and each pair can only move as quickly as its slowest member. 

Their pursuer is likely not far behind.  What is the quickest way to get everyone across the bridge?

Dots and Rows

This is an old one my dad told me, though I've also heard it as a CarTalk puzzler before:

Above is a straight row of 4 dots: it is a 4-dot row.
Next, we have a set of 13 dots that creates 5 different 4-dot rows.

 

Now again create 5 different 4-dot rows, but using only 10 dots.  Rows must be straight.  Oh, and before you tricksters try giving me a single long string of dots, a 5-dot row does not count as 2 4-dot rows.  You can use a dot multiple times, but rows can't overlap.

Cubic Calendar

From http://www.folj.com/puzzles/

A corporate businessman has two cubes on his office desk. Every day he arranges both cubes so that the front faces show the current day of the month.

What numbers are on the faces of the cubes to allow this?

Note: You can't represent the day "7" with a single cube with a side that says 7 on it. You have to use both cubes all the time. So the 7th day would be "07".

A Lost and Hungry Vagabond

This is from the Car Talk Puzzler:
A lost and hungry vagabond happened upon a pair of travelers one of whom had three loaves of bread while the other had five. All of the loaves were the same size and weight.

The two travelers decided to share their bread with the vagabond, and that the eight loaves should be shared equally among the three of them. When they had finished, the vagabond reached into his pocket and pulled out eight coins. He handed three coins to the traveler who had had the three loaves and five to the other one and disappeared into the inky shadows.

The next morning, right after no breakfast, the one who had received the three coins said to the other one, 'I don't think he should have given three coins to me and five to you. It's not fair.' And he was right. How should the coins have been split up?

The Camels

Borrowed from http://www.folj.com/puzzles/

Four tasmanian camels traveling on a very narrow ledge encounter four tasmanian camels coming the other way.

Tasmanian camels never go backwards, especially when on a precarious ledge. The camels will climb over each other, but only if there is a camel sized space on the other side.

The camels didn't see each other until there was only exactly one camel's width between the two groups.

How can all camels pass, allowing both groups to go on their way, without any camel reversing?

Hint: to help visualize, use paper clips or coins.