T2B59

This is one of my favourites:

DO NOT USE A CALCULATOR, USE MENTAL MATH.

Take 1000 and add 40.

Now take that number and add 1000 and 30.

Add your answer to 1000 and 20.

Finally, add 1000 and 10.

What number do you get?

T2B58

The man had sweetened his original cup of coffee before he gave it to the waiter. Upon tasting it and discovering it was still sweet, he realized the waiter just took the fly out instead of giving him a new coffee.

T2B57

This is one of my favourite riddles.

A man, upon ordering and receiving a coffee, discovers a fly in it. He sends it back to the kitchen, but when the waiter brings a new cup of coffee to him, he says, "This is the same cup of coffee with the fly removed." How did he know?

T2B56

Applied Skills Care Packages Paragraph:

I made five packages, each with different contents. In each, I put a knitted scarf, except for one where I included a hat. I put a toothbrush and toothpaste kit in one of them, a shaving kit in two of them, and a comb in two of them. I also put a small hand towel, a bar of soap and a small shampoo and conditioner in each of them. I thought to include these to make it easier for the homeless to get clean at the end of the day. I put a variety of cookies, granola bars, and Pocky (basically, healthy snack food) in a small Ziploc bag inside the large Ziploc bag, in case they get hungry. I think by challenging us to think what we would want in a care package as a homeless person, Mr. Olson really forced us to think from a different perspective and that was really powerful.

Also, the answer to the last riddle was tilt it so the water lines up with the edge of the bottom of the glass (45 degrees) and if the water matches the opposite edge on the top it is half full.

T2B55

This is a cool riddle:

You have a glass of water that looks about half full. How can you tell, only using the glass of water itself, if the glass is half full or not?

The glass is a right cylinder.

T2B54

WHY. IS. THIS. RIDDLE. SO. HARD.

 A king finds a woman he wants to marry but she refuses. But since he is the king, she has to. The king gives her a deal: he will write 'YES' and 'NO' on two pieces of paper. The papers will be put into a hat and she will choose one. If it says yes she will marry him, if it says no she will not. The only problem is that the king cheats and puts two pieces of paper that say yes into the hat, but the woman is the only one who sees this.

How can the woman avoid marrying the king?

T2B53

This is the best solution that I've found, because it's very clear:

To understand the answer, we need to reduce this problem to only 2 pirates. So what happens if there are only 2 pirates. Pirate 2 can easily propose that he gets all the 100 gold coins. Since he constitutes 50% of the pirates, the proposal has to be accepted leaving Pirate 1 with nothing.

Now let’s look at 3 pirates situation, Pirate 3 knows that if his proposal does not get accepted, then pirate 2 will get all the gold and pirate 1 will get nothing. So he decides to bribe pirate 1 with one gold coin. Pirate 1 knows that one gold coin is better than nothing so he has to back pirate 3. Pirate 3 proposes {pirate 1, pirate 2, pirate 3} {1, 0, 99}. Since pirate 1 and 3 will vote for it, it will be accepted.

If there are 4 pirates, pirate 4 needs to get one more pirate to vote for his proposal. Pirate 4 realizes that if he dies, pirate 2 will get nothing (according to the proposal with 3 pirates) so he can easily bribe pirate 2 with one gold coin to get his vote. So the distribution will be {0, 1, 0, 99}.

Smart right? Now can you figure out the distribution with 5 pirates? Let’s see. Pirate 5 needs 2 votes and he knows that if he dies, pirate 1 and 3 will get nothing. He can easily bribe pirates 1 and 3 with one gold coin each to get their vote. In the end, he proposes {1, 0, 1, 0, 98}. This proposal will get accepted and provide the maximum amount of gold to pirate 5.

T2B52

This is such an awesome and difficult riddle.

Five pirates are parting ways after finding a treasure of 100 pieces of gold. The pirates decide to split it based on a vote. Each pirate, from oldest to youngest, gets to propose a plan on how to split the gold.

If at least 50 percent of the other remaining pirates agree on the plan, that is how they will split the gold. If less than 50 percent of the pirates agree, the pirate who came up with the plan will be thrown overboard. Each pirate is smart, greedy, and wants to throw as many others overboard as possible without reducing the amount of gold they get.

What plan can the first (oldest) pirate propose to live and get as much gold as possible?

T2B51

The answer is neither: The yolk of an egg is yellow.

Although, grammatically, it is is.

T2B50

I love this one because it's exactly the type of thing I always fall for.

Is it correct to say, "The yolk of the egg is white", or, "The yolk of the egg are white"?

T2B49

Lateral thinking skills:

Jim and his wife Patty were sitting in bed together one evening while a thunderstorm raged outside. After a bolt of lightning followed by a loud clap of thunder, the lights went out. Jim stopped reading and went to sleep, but Patty continued reading without using any device with batteries. How did she do it?

Answer:
Patty is blind and was reading a Braille book so she didn’t need the light to begin with. Of course this also meant she didn’t know Jim snuck downstairs to get some cookies, but we’ll just keep that quiet.

T2B48

This is a bit confusing at first, but it's good logic:

A taylor can make a pair of pants from the scraps left over from sewing up five pairs of pants. If he has twenty-five scraps, how many pairs of pants can he make?

Answer:
Six pairs of pants. He can make five initially, but once he’s done making five pairs of pants, he’ll have five remaining sets of scraps, meaning he can make an additional pair of pants, totaling six.

T2B47

An 18-wheeler is crossing a 4 kilometer bridge that can only support 10,000 kilograms and that’s exactly how much the rig weighs. Halfway across the bridge a 30 gram sparrow lands on the cab, but the bridge doesn’t collapse. Why not?

Since the bridge is 4 kilometers long, the halfway point would be 2 kilometers. The 18-wheeler would have used much more than 30g of fuel to drive 2 kilometers.

I guess it depends on your car model.

T2B46

The answer is 2. The reason behind it is the number of closed circles in the 4 digit number. 8 has 2, 6, 9, and 0 all have one.

T2B45

T2B43's riddle looks a bit messed up, I'll fix it:

This problem can be solved by preschool children in five to ten minutes, by programmers in an hour and by people with higher education…well, check it yourself.

8809 = 6
7111 = 0
2172 = 0
6666 = 4
1111 = 0
3213 = 0
7662 = 2
9313 = 1
0000 = 4
2222 = 0
3333 = 0
5555 = 0
8193 = 3
8096 = 5
1012 = 1
7777 = 0
9999 = 4
7756 = 1
6855 = 3
9881 = 5
5531 = 0
2581 = ?

What is the missing number and why?

Ta-da!

T2B44

This is so smart.

Ida puts her coffee into the microwave, as she does every morning, for exactly two minutes. When the microwave goes off, she opens the door, but then closes the door again and sets the microwave for two more seconds. What good would two more seconds be?

Answer:

To rotate the handle on the mug so she can comfortably remove it.

I've never thought of that before, maybe I should try doing that. :P

T2B43

I'VE FINALLY DONE IT!

I'VE CRACKED THIS RIDDLE!

HOORAY!

It took me ages to finally find a pattern.

This problem can be solved by preschool children in five to ten minutes, by programmers in an hour and by people with higher education…well, check it yourself.

8809 = 6

7111 = 02172 = 06666 = 41111 = 03213 = 07662 = 29313 = 10000 = 42222 = 03333 = 05555 = 08193 = 38096 = 51012 = 17777 = 09999 = 47756 = 16855 = 39881 = 55531 = 02581 = ?

What is the missing number and why?

T2B42

This riddle has been driving me CRAZY!

U2 has a concert that starts in 17 minutes and they must all cross a bridge to get there. All four men begin on the same side of the bridge. You must help them across to the other side. It is night. There is one flashlight. A maximum of two people can cross at one time. Any party who crosses, either 1 or 2 people, must have the flashlight with them.

The flashlight must be walked back and forth. It cannot be thrown and other tricks like that are not needed to solve the problem. The solution is simply a matter of allocating resources in a certain order. Each band member walks at a different speed. A pair must walk together at the rate of the slower man’s pace:

Bono: 1 minute to cross

Edge: 2 minutes to crossAdam: 5 minutes to crossLarry: 10 minutes to cross

For example: if Bono and Larry walk across first, 10 minutes have elapsed when they get to the other side of the bridge. If Larry then returns with the flashlight, a total of 20 minutes have passed and you have failed the mission.

There's no answer on the site that I used, either, but I'm NOT going to look for it until I get it. 

T2B41

I forgot to post the answer to T2B38's riddle.

Whoops.

It's his son.

The reasoning is that the statement "this man's father is my father's son" says that the father of the man in the picture is his father's son. If he has no brothers or sisters, his father's son must be himself, therefore the father of the man is him. If he is father to the man in the picture, then the man must be his son. 

T2B40

Brain Teaser:

A London cab driver picked up a lady who was a notorious chatterbox. He did not want to engage in conversation, so he pretended to be deaf and dumb. He pointed to his mouth and ears to indicate that he could neither speak nor hear. After she alighted, he pointed to the meter so that she could see how much she owed. She paid him and walked off. Then she realized that he could not have been a deaf mute. How did she know?

Answer:

He couldn't be deaf as he must have heard her instructions when she entered his taxi or he wouldn't have known where to take her. 

T2B39

New brain teaser:

King Ferdinand has no immediate living relatives and decides to hold a contest to find a worthy successor when he dies. He gives a seed to every contestant and explains that the person with the healthiest and most beautiful plant will win the throne.

When the final day of the contest arrives, the king finds hundreds of plants of all shapes and sizes. However, he ignores them and awards the throne to a girl holding a pot with only moist dirt.

Why did she win?

Answer:

King Ferdinand was a kind and trusting man and wanted to be sure he found an honest heir. He gave small pebbles to all the contestants, claiming they were seeds. Therefore, any contestant with a plant had switched their “seed” in order to win. Everyone but the girl had been dishonest.

T2B38

This is a classic riddle (answer next blog):

A man is looking at a picture of a man on the wall and states, “Brothers and sisters I have none, but this man’s father is my father’s son.”

Who is the man in the picture in relation to the man looking at the picture?

T2B37

This is really good:

What do the following words have in common?

current
by
dew
faze
loan
ate

Answer:

They all have homonyms:

currant (current)
buy (by)
due (dew)
phase (faze)
lone (loan)
eight (ate)

T2B36

My friend told this to me once, and I've heard it a lot of times before. It's fairly simple once you think about it, so I won't say the answer.

A murderer is condemned to death. He has to choose between three rooms to go into. The first is full of raging fires. The second is full of assassins with loaded guns. The third is full of lions that haven't eaten in 3 years. Which room should he pick?

T2B35

This is a cute twist on the classic "apple and oranges" puzzle.

http://www.techinterview.org/post/526310513/jelly-beans

The mechanical parts of writing aren't very good, but it's readable.

You have three jars that are all mislabeled. one contains peanut butter jelly beans, another grape jelly jelly beans, and the third has a mix of both (not necessarily a 50/50 mix, could be a 1/99 mix or a 399/22 mix). how many jelly beans would you have to pull out, and out of which jars, to find out how to fix the labels on the jars?

|     |        |     |          |     |
|jar 1|        |jar 2|          |jar 3|
|     |        |     |          |     |
=======        =======          =======
  p.b.          grape          p.b./grape

thanks to joel wollman

Solution

You have three jars that are all mislabeled. one contains peanut butter jelly beans, another grape jelly jelly beans, and the third has a mix of both (not necessarily a 50/50 mix, could be a 1/99 mix or a 399/22 mix). how many jelly beans would you have to pull out, and out of which jars, to find out how to fix the labels on the jars?

   |     |                  |     |                 |     |
  |jar 1|                |jar 2|               |jar 3|
   |     |                  |     |                 |     |
=======        =======          =======
     p.b.                   grape             p.b./grape

solution: 1 jelly bean from the p.b./grape jar will do the trick.

the trick here is to realize that every jar is mislabeled. therefore you know that the peanut butter jelly bean jar is not the penut butter jelly bean jar, and the same goes for the rest.

you also need to realize that it is the jar labeled p.b./grape, labelled as the mix jar, that is your best hope. if you choose a jelly bean out of there, then you will know whether that jar is peanut butter or grape jelly jelly beans. it can’t be the mix jar because i already said that every jar is mislabeled.

once you know that jar 3 is either peanut butter, or grape jelly, then you know the other jars also. if it is peanut butter, then jar 2 must be mixed because it can’t be grape (as its labelled) and it can’t be peanut butter (that’s jar 3). hence jar 1 is grape.

if jar 3 is grape, then you know jar 1 must be the mix because it can’t be p.b. (as its labelled) and it can’t be grape (that’s jar 3). hence jar 2 is peanut butter.

if you pick jelly beans from jar 1 or jar 2, then you would have to pick out ALL of the jelly beans before you knew what that jar was. this is because jar 1 and 2 could be the mix, so in order to disprove that they were the mix, you would have to pull out EVERY jelly bean just to make sure (since there could just be one bean of the opposite flavor in there)

T2B34

Short riddle:

Two men, Mr. Smith and Mr. Jones were on a business trip. They stayed at the same hotel, in adjacent rooms. At night, Mr. Jones got into bed and, very soon, fell soundly asleep. Mr. Smith, however, lay in bed for hours, unable to fall asleep. Finally, he got up, phoned Mr. Jones, and, after a while, without saying anything, hung up again. A short while later, Mr. Smith was able to fall asleep.

What explanation can you come up for this?

Answer will be come tomorrow.

T2B33

The answer to the "What Went Wrong?" problem:

70. _______________________
The suitor should have realized that without any informa­ tion given about the truth or falsity of any of the sentences, nor any information given about the relation of their truth­ values, the sentences could say anything, and the object (portrait or dagger, as the case may be) could be anywhere. Good heavens, I can take any number of caskets that I please and put an object in one of them and then write any inscriptions at all on the lids; these sentences won't convey any information whatsoever. So Portia was not really lying; all she said was that the object in question was in one of the boxes, and in each case it really was.
The situation would have been very different with any of the previous Portia stories, if the object had not been where the suitor figured it out to be; in this case one of the old Portias would have had to have made a false statement somewhere along the line (as we will soon see).
Another way to look a t the matter i s that the suitor' s error was to assume that each of the statements was either true or false. Let us look more carefully at the first test of Portia Nth, using two caskets. The statement on the gold casket, "The portrait is not in here," is certainly either true or false, since either the portrait is in the gold casket or it isn't. It happened to be true, as a matter of fact, since Portia had actually placed the portrait in the silver casket. Now, given that Portia did put the portrait in the silver casket, was the statement on the silver casket true or false? It couldn't be either one without getting into a paradox! Suppose it were true. Then exactly one of the statements is true, but since the first statement (on the gold casket) is true, then this statement is false. So if it is true, it is false.
On the other hand, suppose this statement on the silver casket is false. Then the first is true, the second is false, which means that exactly one of the statements is true, which is what this statement asserts, hence it would have to

. be true! Thus either assumption, that the statement is true or is false, leads to a contradiction.
It will be instructive to compare this test with the second test given by Portia III, which also used just two caskets. The gold casket said the same thing as the gold of the problem, "The portrait is not in here," but the silver casket, instead of saying "Exactly one of these two state­ ments is true," said "Exactly one of these two caskets was fashioned by Bellini." Now, the reader may wonder what significant difference there is between these two state­ ments, giventhatBelliniinscribed onlytrue statements and Cellini only false ones. Well, the difference, though subtle, is basic. The statement, "Exactly one of these two caskets was fashioned by Bellini" is a statementwhich must be true or false; it is a historic statement about the physical world­ either it is or it is not the case that Bellini made exactly one of the two caskets. Suppose, in the Portia III problem, that the portrait had been found to be in the silver casket instead of the cold casket. What would you conclude: that the statement on the silver casket was neither true nor false? That would be the wrong conclusion! The statement, as I have pointed out, really is either true or false. The correct conclusion to draw is that if the portrait had been in the silver casket, then Portia In would have been lying in saying what she did about Bellini and Cellini. By contrast, the modern Portia could place the portrait in the silver casket without having lied, since she said nothing about the truth-values of the statements.
The whole question of the truth-values of statements which refer to their own truth-values is a subtle and basic aspect of modern logic and will be dealt with again in later chapters.