Brainteasers that can drive you crazy!

Brainteasers that can drive you crazy!

How many faces can you see?

The four questions below are Mensa brainteasers:

Number 1:
Prior to a sale 17 tee shirts sold at £8 each.
The Summer sale began and a further 85 tee shirts were sold at a reduced price.
The average amount paid for each tee shirt over the whole time was £6.
What was the sale price?

Number 2:

Two cars set off from the same point to travel the same journey.
The first car sets off two minutes before the second car. If the first car travels at 40km/h and the second car travels at 90km/h, how many kilometres from the starting point will they draw level?

Number 3:
A coach covers its outward journey at 50 mph.
It returns, over exactly the same distance at 33.3333 mph.
What is the average speed of the coach over the entire journey?

Number 4:
A car journey is spread over five hours.
In the first hour one third of the total distance is covered.
The next hour, the car completes one third of the remaining distance.
The following hour one quarter of the remainder is covered and in the last hour the car covers half of the remaining distance.
There is now 10 miles remaining.
How many miles has the car travelled?


What is the parking spot number that the parked car occupies?
(The answer is at the bottom of this page).

How do you link these nine dots in four straight lines without lifting your pen?
(The answer is at the bottom of this page).

If it takes five machines five minutes to make five widgets, how long would it take 100 machines to make 100 widgets?
(The answer is at the bottom of this page).

Cheryl's Birthday Puzzle

Another exercise in logical deduction and analytical thinking. If you are an expert in Sudoku puzzles you will be familiar with the idea of using given clues to eliminate alternatives in order to get closer to the solution, which is quite the case here.
Albert and Bernard just became friends with Cheryl, and they want to know when her birthday is. Cheryl gives them a list of 10 possible dates:
May 15 16 19
June 17 18
July 14 16
August 14 15 17
Cheryl then tells Albert and Bernard separately the month and the day of her birthday, respectively.
Albert: I don't know when Cheryl's birthday is, but I know that Bernard does not know, too.
Bernard: At first, I didn't know when Cheryl's birthday is, but I know now.
Albert: Then I also know when Cheryl's birthday is.
When is Cheryl's birthday?

Ten questions

Here are 10 questions that might not test your intelligence so much as your ability to "think out of the box" (the answers are given immediately below):
1. A man lives on the 28th floor of a high-rise building. Every day he gets the lift down to the ground floor to leave the building to go to work. Upon returning from work he always gets down at the 26th floor and has to climb the other two floors - unless it's raining! Why?
2. A man and his son are in a car accident. The father dies on the spot, but the boy is rushed to the hospital. When he arrives the surgeon says, "I can't operate on this boy, he is my son!" How can this be?
3. A woman had two sons who were born on the same hour of the same day of the same year. But they were not twins. How could this be so?
4. A murderer is condemned to death. He has to choose between three rooms. The first is full of raging fires, the second of assassins with loaded guns, and the third of lions that haven't eaten in 3 years. Which room is the safest for him to go to?
5. Can you name three consecutive days without using the words Monday, Tuesday, Wednesday, Thursday, Friday, Saturday, or Sunday? (or day names in any other language)
6. 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?
7. There are six eggs in the basket. Six people each take one of the eggs. How can it be that one egg is left in the basket?
8. Anthony and Cleopatra are lying dead on the floor of a room. Nearby is a broken bowl. There is no mark on either of their bodies and they were not poisoned. How did they die?
9. The boss of a storage warehouse had just arrived at work when one of his employees burst into his office. The man said that while asleep in the building the previous night he had dreamt that one of the stored boxes contained a bomb which would explode at two p.m. The boss was sceptical, but agreed to investigate. After a search, a bomb was truly found in the area foreseen in the man's dream. The police were called to defuse the bomb and thus a tragedy was averted. Yet afterwards, the boss after thanking the employee profusely, fired him. The sacked man had not planted the bomb, and his prophetic dream had saved the warehouse from a tragedy. Yet the manager was right to fire him. How could that be so?
10. A poor servant in a village was told by his master that he could wish for anything he wanted. It could be any wish at all but just one. The servant asked his mother what she wanted and she said she wanted a TV set. Next, the servant asked his wife who said she wanted a microwave. Finally, the servant went to his father who wanted a bicycle. The next day he went to his master and made one wish through which his mother, father and wife each got what they wanted. What was his wish?

Answers to the above 10 questions

1. The man is very short and can only press the button for the 26th floor. However, if it is raining then he will have his umbrella with him to press the higher button.
2. The surgeon was his mother (this is the type of questions you should watch out for in an interview, especially if the interviewer is a woman!)
3. They were two of a set of triplets (the third being a girl). Of course they can also be two of quadruplets, etc.).
4. The third. Lions that haven't eaten in three years would certainly have been dead.
5. Yesterday, Today, and Tomorrow!
6. 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.
7. The last person took the basket with the last egg still inside.
8. Anthony and Cleopatra were actually the names of two goldfish. The bowl was knocked over by a cat and they were left without water.
9. Because he was the night watchman (or some other night shift worker) and had been sleeping on his job.
10. Since it could be any wish at all, he asked for three wishes, thus satisfying everybody! Of course he could also simply ask for a sum large enough to allow him to buy all the three items.

Unless otherwise stated all the answers to the brainteasers below are to be found in this page.

Go here for some 44 questions based on lateral thinking used at job interviews.

Tytamayo from Texas has sent me this riddle, saying it is driving her absolutely crazy:

There are 7 girls in a bus. Each girl has 7 backpacks. In each backpack, there are 7 big cats. For every big cat there are 7 little cats. Question: How many legs are there in the bus?
Assuming that this is a straightforward mathematical problem and that there is no one else in the bus, see if you can account for 10,990 legs?

Suleiman Garba Sulei of Bayero University, Kano, Nigeria, sent me the following brainteaser:

In northern Nigeria there was a man who had 68 big camels and 3 sons Babangida the 1st born, Tanko, the 2nd born and Jatau, the last born. As he was about to die, he uttered his last words as follows: "If I die, Babangida, I don't like any lawyer to divide those camels as irrationally as the way he may like. So tell him this is how I want the camels to be divided among the three of you: You take half of the camels, Tanko takes one-third (1/3) and Jatau takes one-ninth (1/9) of the camels. That's how I like it, Babangida, no other way; don't let any of the camels be slaughtered and its meat be divided because it's against the rule of our forefathers to slaughter any of the camels."
If you were the lawyer, how can you divide the camels as their father wanted it?

How sharp are your eyes?

There is no catch in this but you need to have very sharp eyes. See if you can find them all in under one minute (without using the cursor to help).

1. First find the C below.

2. Now find the 6 below.

3. And finally try to find the N below.
Grateful thanks to Sumayya Essack for sharing.

3 men in a motel (the missing dollar)

I have a brainteaser that's been teasing my brain for some time now. I am hopeful that you will have an answer.
3 men go into a motel. The desk clerk said the room was $30, so each man paid $10 and went to the room. A while later, the desk clerk realized the room was only $25, so he sent the bellboy to the 3 guys' room with $5. On the way, the bellboy couldn't figure out how to split $5 evenly between 3 men so he gave each man $1 and kept the other $2 for himself. This meant that the 3 men each paid $9 for the room, which made a total of $27. Add to that the $2 the bellboy kept and the total is $29. Where is the other dollar?
- From Richard A. Feimer (message received by email)
Mr. Feimer has agreed to share this brain-teaser with others. Try to look at the problem from different angles.

Riddle of the 4 persons crossing a lake
Here is another brainteaser from Suleiman Garba Sulei of Bayero University, Kano, Nigeria:

Four persons must cross a large lake to get back to their respective village. The 1st person sees the lake, touches its shallow water and crosses it safely. The 2nd person sees the lake, never touches its water but crosses it more safer than the 1st person and the last two persons don't even see the lake, never touch its water but they crossed it nevertheless.

Names are not what they claim to be!
(Thanks to Shirley Han for sharing).
1) How long did the Hundred Years War last?
2) Which country makes Panama hats?
3) From which animal do we get catgut?
4) In which month do Russians celebrate the October Revolution?
5) What is a camel's hair brush made of?
6) The Canary Islands in the Pacific is named after what animal?
7) What was King George VI's first name?
8) What color is a purple finch?
9) What is the color of the black box in a commercial airplane?

A riddle for you (answer below*):
When is a door not a door?

Another 12 brainteasers

NOTE: Some of the questions below need some thinking (mostly lateral thinking), others need no thinking at all, and as for the rest, you will never be able to find the answers if you think too hard!

1. There is no catch to this question but can you find the answer without using your calculator but through logical reasoning alone? Of the 800 women in an African village, 3% wear just one earring. Half of the remaining 97% wear two earrings while the other half don't wear any earring at all. What is the total number of earrings worn by the women in the village?

2. There are only two barbers in a small village and they have their shops opposite each other. A logician passing by saw that the first barber's shop was untidy, the barber himself was unkempt and had a lousy haircut. The barbershop opposite was clean and the barber was tidy and well-shaven yet he preferred to have his hair cut by the first barber. Why was this?

3. At a restaurant a customer found a fly in his cup of coffee just as he was about to drink it and asked the waiter to have it changed. When the waiter came back he took a sip and told the waiter: "This was the same cup that I had earlier." How did he know?

4. We were born of the same mother, on the same day, at the same hour and in the same year. Yet we are not twins. How do you explain this?

5.Two fathers and two sons were seated round a table. There were four apples on the table. Each of them took one apple and ate it entirely yet there was still one apple left on the table. How was this possible?

6. Before Mount Everest was discovered which was the highest mountain in the world?

7. Here everything is not always in order. For example, Friday comes before Thursday, the cart comes before the horse, the driver comes before the employer. Where are we?

8. In a drawer are 20 red socks and 20 black socks in complete disorder. If a man gropes in the dark and opens the drawer what is the smallest number of socks he must take out to be sure that he has one pair of the same colour?

9. When I am alive I stay put where I am. It is only when I am dead that I move about here and there. Who am I?

10. How can you be behind a person when that person is also behind you?

11. I am never the first to speak but I am always the last to be heard. Who am I?

12. Jack was piloting a plane behind a car but was never able to overtake it. Why?

Given up trying? Need to know the answers to all the brainteasers in this page? Go here.

Answer to the riddle:
When is a door not a door?

¡ɹɐɾɐ sᴉ ʇᴉ uǝɥM*

Answer to the riddle:
If it takes five machines five minutes to make five widgets,
how long would it take 100 machines to make 100 widgets?
sǝʇnuᴉɯ ϛ

The parked car occupies number 87. This is another example where you have to think out of the box!

Answer to the 9 dots riddle.

Or perhaps the above riddles were all too easy for you? Then go here for Brainteasers 2.