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December 21, 2015

Lateral Thinking Riddle

On a windy rainy night , I was driving in my car. When i reach the bus stand , i see three people waiting for the bus.

1. An old lady who needs an immediate medical attention
2. My Best Friend
3. Girl whom i love from childhood

My car is a two seater, so can you tell me , what i have done in this situation ?

December 4, 2015

November 26, 2015

100 Coins Puzzle

You have a 100 coins laying flat on a table, each with a head side and a tail side. 10 of them are heads up, 90 are tails up. You can't feel, see or in any other way find out which side is up. Split the coins into two piles such that there are the same number of heads in each pile.

November 10, 2015

10 Cigaratte Butts Puzzle

Bruce is an inmate in a large prison, and like most of the other prisoners, he smokes cigarettes. During his time in the prison, Bruce finds that if he has 3 cigarette butts, he can cram them together and turn them into 1 full cigarette. Whenever he smokes a cigarette, it turns into a cigarette butt.
One day, Bruce is in his cell talking to one of his cellmates, Steve.
"I really want to smoke 5 cigarettes today, but all I have are these 10 cigarette butts," Bruce tells Steve. "I'm not sure that will be enough."
"Why don't you borrow some of Tom's cigarette butts?" asks Steve, pointing over to a small pile of cigarette butts on the bed of their third cellmate, Tom, who is out for the day on a community service project.
"I can't," Bruce says. "Tom always counts exactly how many cigarette butts are in his pile, and he'd probably kill me if he notices that I had taken any."
However, after thinking for a while, Bruce figures out a way that he can smoke 5 cigarettes without angering Tom. What is his plan?

November 3, 2015

Count the Number of Squares

There are three squares in the picture and it is overlapping and forms 2 more squares.
What is the greatest number of squares you can make by overlapping three squares of the same size?

October 28, 2015

Palindromic Clock

On a 12-hour digital clock, what is the smallest interval between two times that are palindromic (can be read forwards and backwards as the same number)?

October 22, 2015

Peculiar Number Puzzle

I just found a number with an interesting property:
When I divide it by 2, the remainder is 1.
When I divide it by 3, the remainder is 2.
When I divide it by 4, the remainder is 3.
When I divide it by 5, the remainder is 4.
When I divide it by 6, the remainder is 5.
When I divide it by 7, the remainder is 6.
When I divide it by 8, the remainder is 7.
When I divide it by 9, the remainder is 8.
When I divide it by 10, the remainder is 9.

It's not a small number, but it's not really big, either.
Find the smallest number with such property.

October 8, 2015

12 men on an island riddle

There is an island with 12 islanders. All of the islanders individually weigh exactly the same amount, except for one, who either weighs more or less than the other 11.
You must use a see-saw to figure out whose weight is different, and you may only use the see-saw 3 times. There are no scales or other weighing device on the island.

How can you find out which islander is the one that has a different weight?

October 1, 2015

100 employees in a conference room

There are 100 employees in a conference room in New York City. You note that 99% of them are managers. How many managers would need to leave the conference in order to reduce the percentage of managers in the hall to 98%?

September 17, 2015

A Probability Problem With Pearls

"I'm a very rich man, so I've decided to give you some of my fortune. Do you see this bag? I have 5001 pearls inside it.
2501 of them are white, and 2500 of them are black. No, I am not racist. I'll let you take out any number of pearls from the bag without looking.
If you take out the same number of black and white pearls, I will reward you with a number of gold bars equivalent to the number of pearls you took."

How many pearls should you take out to give yourself a good number of gold bars while still retaining a good chance of actually getting them?

September 10, 2015

Probability Heaven Puzzle

A person dies, and he arrives at the gate to heaven. There are three doors in the heaven. one of them leads to heaven. another one leads to a 1-day stay at hell, and then back to the gate, and the other leads to a 2-day stay at hell, and then back to the gate. every time the person is back at the gate, the three doors are reshuffled. How long will it take the person to reach heaven?

September 2, 2015

Birthday Puzzle

The day before yesterday I was 25 and the next year I will be 28. This is true only one day in a year. What day is my birthday?

August 1, 2015

Two Paper Cubes Puzzle

A man has two paper cubes on his desk. Every day he arranges both cubes so that the front faces show the current day of the month. What numbers are required on the faces of the cubes to allow this for all possible days in the calendar?

July 23, 2015

Misfortune Clock

You have the misfortune to own an unreliable clock. This one loses exactly 20 minutes every hour. It is now showing 4:00am and you know that is was correct at midnight, when you set it. The clock stopped 4 hours ago, what is the correct time now?

July 6, 2015

Probability Puzzle: Tossing of Coins

A man tosses three coins in the air. When they land, he finds that two of the coins have heads up and one has tails up. What is the probability that when the coins are tossed again, they will land again with two heads up and one tails up.

Please note that the coins are unbiased.

June 19, 2015

Number Comparisons

You have 32 numbers. What is the least number of comparison needed to find the 2nd smallest out of them?

May 28, 2015

8 Queens on a Chessboard Puzzle

In chess, queens can move horizontally, vertically, or diagonally, as far as they like, as shown in the picture. We say that a queen can "attack" another piece if it can move into the other piece on the next move. How can you place 8 queens on a chessboard such that none of the queens can attack each other?

May 2, 2015

Which Clock is Better ?

Which clock works better?
The one that loses a minute a day or the one that doesn't work at all?

April 24, 2015

Sum and Product Puzzle

X and Y are two different integers, greater than 1, with sum less than or equal to 100. S and P are two mathematicians; S knows the sum X+Y, P knows the product X*Y, and both are perfect logicians. Both S and P know the information in these two sentences. The following conversation occurs:

S says "P does not know X and Y."
P says "Now I know X and Y."
S says "Now I also know X and Y!"

What are X and Y?

April 16, 2015

Singapore Birthday Problem : When is Cheryl's Birthday ?

Albert and Bernard just met Cheryl. “When’s your birthday?” Albert asked Cheryl.

Cheryl thought a second and said,
“I’m not going to tell you, but I’ll give you some clues.”
She wrote down a list of 10 dates:

May 15, May 16, May 19
June 17, June 18
July 14, July 16
August 14, August 15, August 17

“My birthday is one of these,” she said.
Then Cheryl whispered in Albert’s ear the month and only the month of her birthday.

To Bernard, she whispered the day, and only the day of her birthday.

“Can you figure it out now?” she asked Albert.

Albert: I don’t know when your birthday is, but I know Bernard doesn’t know, either.
Bernard: I didn’t know originally, but now I do.
Albert: Well, now I know, too!

When is Cheryl’s birthday?


Lets first analyze all the given birth dates. The dates can be easily viewed as

Now will analyze the conversation in detail

Line 1) Albert Says: I don’t know when Cheryl’s birthday is, but I know that Bernard doesn’t know too.
All Albert knows is the month, and every month Cheryl mentioned has more than one possible date, so of course he doesn’t know when her birthday is.

The only way that Bernard could know the date with a single number, however, would be if Cheryl had told him 18 or 19, since of the ten date options only these numbers appear once, as May 19 and June 18.

For Albert to know that Bernard does not know, Albert must therefore have been told July or August (not June or May), since this rules out Bernard being told 18 or 19.

Thus, only possible months for Albert are : July and August
And, only possible days for Bernard are : 14, 15, 16 and 17

Thus, the solution space is now reduced to :
Line 2) Bernard: At first I don’t know when Cheryl’s birthday is, but now I know.

Bernard has deduced that Albert has either August or July. If he knows the full date, he must have been told 15, 16 or 17, since if he had been told 14 he would be none the wiser about whether the month was August or July. Each of 15, 16 and 17 only refers to one specific month, but 14 could be either month.

Thus, the solution space is now reduced to :

Line 3) Albert: Then I also know when Cheryl’s birthday is.

When Albert says that he also knows the answer, he doesn't have the Bernard's data still ! He doesn't know that the day with Bernard is 15, 16 or 17. Then, how did he came to conclusion that he also knows the answer. That means he has July as month as there is only one day associated with July. So, he is sure that now I also know the answer.

The answer, therefore is July 16.

April 13, 2015

5, 15, 1115, 3115, 132115, 1113122115, 311311222115, ?

What is the next number in this sequence:

5, 15, 1115, 3115, 132115, 1113122115, 311311222115, ?

April 10, 2015

True and False Statements

Which of the following statements are true and which are false?
1. Only one of the statements is false.
2. Exactly two of the statements are false.
3. Only three of the statements are false.
4. Exactly four of the statements are false.
5. All five of these statements are false.

March 29, 2015

Birbal Solves Farmer’s Well Dispute

A farmer and his neighbor once went to Emperor Akbar’s court with a complaint. “Your Majesty, I bought a well from him,” said the farmer pointing to his neighbor, “and now he wants me to pay for the water.” “That’s right, your Majesty,” said the neighbor. “I sold him the well but not the water!” The Emperor asked Birbal to settle the dispute.
How did Birbal solve the dispute in favor of the farmer?

March 24, 2015

The Greek Philosophers

One day three Greek philosophers settled under the shade of an olive tree, opened a bottle of Retsina, and began a lengthy discussion of the Fundamental Ontological Question: Why does anything exist?

After a while, they began to ramble. Then, one by one, they fell asleep.
While the men slept, three owls, one above each philosopher, completed their digestive process, dropped a present on each philosopher's forehead, the flew off with a noisy "hoot." Perhaps the hoot awakened the philosophers.
As soon as they looked at each other, all three began, simultaneously, to laugh.

Then, one of them abruptly stopped laughing. Why?

March 18, 2015

How many 0’s between 1 to 200 ?

How many 0’s are present in numbers from 1 to 200 ?
(including both numbers)

March 10, 2015

4 Tablets Puzzle

If I give you 4 tablets which consist of 2 for fever and 2 for cold.
All 4 being of the same size, shape, taste, weight and color and have no cover. You have to take 1 cold and 1 fever tablet right now.
How will you choose correctly?

March 4, 2015

Poisoned Wine Puzzle

You have 240 barrels of wine, one of which has been poisoned. After drinking the poisoned wine, one dies within 24 hours. You have 5 slaves whom you are willing to sacrifice in order to determine which barrel contains the poisoned wine.
How do you achieve this in 48 hours?

March 3, 2015

Month Puzzle

If January   = 101025
February     = 6525
March         = 13188
April           = 1912
May            = 13125
June           = 10215
July            = ?

March 1, 2015

Wrotten Apple !

An apple is in the shape of a ball of radius 31 mm.
A worm gets into the apple and digs a tunnel of total length 61 mm,
and then leaves the apple. (The tunnel need not be a straight line.)
Prove that one can cut the apple with a straight slice through the center so that one of the two halves is not rotten.

February 26, 2015

Which Letter is Missing ?

Which letter is missing from this sequence:

A , A , A , A , _ , A , A , A , A , A , A ,U

Note: the answer is not A or U.

February 25, 2015

Pick a Good Candy !

How do you place 50 good candies and 50 rotten candies in two boxes such that if you choose a box at random and take out a candy at random, it better be good!
That means probability of choosing a good candy should be highest. There is no restriction in putting the candies in 2 boxes. Any number of candies can be put in any box.

February 24, 2015

World with All Girls !!

In a world where everyone wants a girl child, each family continues having babies till they have a girl.
What do you think will the boy to girl ratio be eventually?
(Assuming probability of having a boy or a girl is the same)

February 23, 2015

Playing with Invisible Dice

You have 2 dice. One regular die and a an invisible die. Numbers 1 to 6 are written on the regular die.But you don't know what's written on the invisible dice.
After tossing both, I speak the sum of outcome of both die. It so happens that the outcome is always an integer between 1 to 12, with equal probability (1/12 each).
Can you guess what are the numbers printed on special invisible dice?

February 19, 2015

Alex bought a bag of apples

Alex bought a bag of apples on Saturday, and he ate a third of them. On Sunday he ate half of the remaining apples.
He ate one more on Monday and one more on Tuesday, and then ate half of the remaining apples on Wednesday. On Thursday he looked in the bag and saw that there was just one apple left.
How many apples did the bag have to begin with?

February 18, 2015

Spiderman's Girlfriends

Spiderman has two girlfriends, Mary Jane & Gwen Stacy.
After completing every mission, he rushes to the central subway. Since spidey is a nice man, much impartial, he takes which-ever train arrives first. From subway, one series go towards Mary's place, and another series move towards Stacy. Trains from either series appear every 10 minutes. Also, Peter Parker sticks with the train which arrives first.
But somehow, he notices that he is spending 9 times more dates with Mary Jane than Stacy. Can you explain why?

Add the Missing Numbers

Put the numbers 6, 10 and 12 to the correct place in the below sequence and make it complete.

1,  2,  4,  5,  9,  3,  7,  8,  11

February 10, 2015

Which of the Triangles fits the Missing Triangle?

Probability of Secret PIN

Suppose everyone in the class chose a secret 3-digit PIN number. What is the probability that everyone chooses a different number? Assume there are 120 students in the class.

February 7, 2015

Three Choices with One Coin

At a restaurant, how could you choose one out of three desserts with equal probability with the help of one single coin?

February 5, 2015

Who is the man's Sister?

A man escapes from jail with help from his girlfriend. Four girls are accused of being the man's girlfriend. His girlfriend is lying. Two girls are innocent and telling the truth. The other girl is the man's sister who is helping the girlfriend lie. Who is the man's sister?

Amanda: "Melinda is his girlfriend."
Vanessa: "Eva is lying."
Eva: "Amanda is lying."
Melinda: "Vanessa is not his sister."

February 2, 2015

Birbal Puzzle: Who was the real king ?

The King of a distant land had heard that Birbal was one of the wisest men in the East and so desired to meet Birbal. He sent Birbal an invitation to visit his country.

In due course, Birbal arrived in the distant kingdom. When he entered the palace he was flabbergasted to find not one but six kings seated there. All looked alike. All were dressed in kingly robes. Who was the real king?

The very next moment he got his answer. Confidently, he approached the king and bowed to him.

How did Birbal know who was the real king?

January 30, 2015

A Farmer Challenges an Engineer a Physicist and a Mathematician.

A farmer challenges an engineer, a physicist, and a mathematician to fence off the largest amount of area on earth using the least amount of fence.

The engineer made his fence in a large circle and said it was the most efficient.

The physicist made a long line and said that the length was infinite. Then he said that fencing half of the Earth was the best.

The mathematician laughed at the others and with his design, beat the others. What did he do?

January 28, 2015

7 Gold Rings Puzzle

You arrive at a hotel and have 3 sets of golden rings. The first set of rings has 4 rings, the second set has 2 rings and the third only has one ring. You cannot take these sets of rings part, You cannot exchange them for a different form of currency, and the hotel clerk has no change. You want to stay at the hotel for 7 nights, and you have to pay one gold ring for each night that you stay. You cannot pay in advance, or all at once at the end of your stay. How do you pay for your 7 nights at the hotel?

January 26, 2015

Parrots and Cages Puzzle

Tina has some parrots and some cages for the parrots.
If she put 4 parrots into each cage then she will have 1 cage left.
If she put 3 parrots into each cage then she will have 1 parrot left over. How many parrots and cages does she have?

January 23, 2015

January 21, 2015

Put any Mathematical signs and get 6.

Put Any Mathematical signs and get 6:
1 1 1 = 6
2 2 2 = 6
3 3 3 = 6
4 4 4 = 6
5 5 5 = 6
6 6 6 = 6
7 7 7 = 6
8 8 8 = 6
9 9 9 = 6

January 11, 2015

Chain and Nail Puzzle

There is a chain nailed to the wall. The chain is 10 feet long and the center of the chain dips down 5 feet from where each side of the chain is nailed to the wall. How far are the 2 ends of chain from each other?

Band around the Earth Puzzle

The circumference of the Earth is approximately 40,000 kilometers, and someone has just made a metal band that circles the Earth, touching the ground at all locations. You come along at night, as a practical joke, and add just 10 meters to its length (one hundredth of one kilometer !) It is now one four-millionth longer, and sits magically just above the ground at all locations How far has it risen ... could a flea, a rabbit or even a man squeeze underneath it?

January 1, 2015

Grandpa's Age Puzzle

Two boys don't know age of each other, one day they met grandpa and asked him about his age. Grandpa said:"The addtion of digit in tens place and the digit in ones place of my age is equal to the subtraction of digit in the tens place and the digit in ones place of age of one of you." The two guys thought hard, but didn't figure it out. The second day, they came to ask grandpa again, grandpa said:"My age is equal to the multiplication of the addition and subtraction of your ages." The two guys could not figure it out. The third day, they came to grandpa, grandpa said:"My age = (age of one of you)*7 - (age of the other)*4" The two poor boys still could not figure it out, the forth day, grandpa said:"One of you, whose age I didn't refer to in the first day, exchange his age's digit in tens place with digit in ones place, then minus the addition of the digit in tens place and the digit in ones place, the result is equal to my age." Can you figure out grandpa's age?