### #1 - Difficult Brain Twister

There are 100 bulbs in a room. 100 strangers have been accumulated in the adjacent room. The first one goes and lights up every bulb. The second one goes and switches off all the even numbered bulbs - second, fourth, sixth... and so on. The third one goes and reverses the current position of every third bulb (third, sixth, ninth… and so on.) i.e. if the bulb is lit, he switches it off and if the bulb is off, he switches it on. All the 100 strangers progresses in the similar fashion.

After the last person has done what he wanted, which bulbs will be lit and which ones will be switched off ?

Ponder over the bulb number 56, people will visit it for every divisor it has. So 56 has 1 & 56, 2 & 28, 4 & 14, 7 & 8. So on pass 1, the 1st person will light the bulb; pass 2, 2nd one will switch it off; pass 4, light it; pass 7, switch it off; pass 8, light it; pass 14, switch it off; pass 28, light it; pass 56, switch it off.
For each pair of divisors the bulb will just end up back in its preliminary state. But there are cases in which the pair of divisor has similar number for example bulb number 16. 16 has the divisors 1 & 16, 2 & 8, 4&4. But 4 is recurring because 16 is a perfect square, so you will only visit bulb number 16, on pass 1, 2, 4, 8 and 16… leaving it lit at the end. So only perfect square bulbs will be lit at the end.

### #2 - Tricky Math Logic Problem

A girl was fond of collecting rare stamps. When she was twenty years old, she bought a box to collect her stamps. On her every birthday, she put 250 stamps in it and her sister who was also fond of collecting stamps took out 50 stamps from it on her birthday. The girl met an accident when she was 60 years old. When her box was opened, there were only 500 stamps in it.

How is it possible logically?

The girl was born on 29 February, thus she put 250 stamps every four years.
In forty years, she put stamps only 10 times which makes the total of 2500 stamps.
Her sister was born on any other day and she took out 50 stamps from the box forty times which makes the total stamp she took out to be 2000.

Thus after forty years, the girl’s box had only 500 stamps.

### #3 - Frog In The Well Riddle

A frog fell on a bottom of the well.
The well is 30 feet deep.

During day time, the frog jumps 5feet while at night when the frog sleeps he slip back 4feet.

In how many days frog will come out from the well ?

26days

In 25days, he will jumo 25feet and den next five feet will make him out of the well

### #4 - Tricky Murder Mystery Logical Riddle

Four boys were playing a game in which they need to throw three stone in the water so that the stone at don't get sunk into the water(there is some solid area in water).
Boy1: Succeeded in throwing 2 stones at solid area but 1 of the stone sunk.
Boy3: All stones got sunk.
Boy4: None of the stones got sunk.

Boy2 was the winner but was struck by a stone in the head and died.

Who killed Boy2 ?

Boy1, he was left with one stone.

### #5 - Infosys Trick Interview Riddle

Bruce Banner was having a candle light dinner with his girlfriend. Suddenly a cold gush of wind entered through the open window and three of the ten candles were extinguished. Assuming that none of the other candles were extinguished.

How many candles are they left with in the end ?

Three.

The candles that were not extinguished will melt down completely eventually. Thus only three candles will remain in the end.

### #6 - Smart Trick Teaser

While preparing the table for dinner, wife came up with an idea to tease his mathematician husband. She asked her husband to pick nine toothpicks and make ten without breaking any toothpick.

The husband was also smart and did it within seconds.

How ?

He aligned the toothpicks to form TEN using one toothpick for each line.

### #7 - Gold Box Puzzle

There are three boxes in a table. One of the box contains Gold and the other two are empty. A printed message contains in each box. One of the message is true and the other two are lies.
The first box says "The Gold is not here".
The Second box says "The Gold is not here".
The Third box says "The Gold is in the Second box".
Which box has the Gold?

As the message contains one truth, the third says that the gold is in the second box, if it is to be true, then the first box message will also become true. So Gold cannot be in second and third boxes. Gold is in the first box.

### #8 - Question Riddle

If in a cycle race, the man who came two places in front of the last man finished one ahead of the man who came fifth, how many contestants were there?

6

### #9 - Truth Or Lie Puzzle

Out of three people (Lavesh, Mayank and Manoj), one of them is a king, one a bureaucrat, and one a thief.

The king always tells the truth, the bureaucrat always lies, and the thief can either lie or tell the truth.

Lavesh says: 'Manoj is a bureaucrat.'
Mayank says: 'Lavesh is a king.'
Manoj says: 'I am the thief.'

Who is the king, who the bureaucrat, and who the thief?

Lavesh is a King
Mayank is a Spy
Manoj is a Bureaucrat

Mayank is not the king, since if he is, then Lavesh would also be the king.
Manoj is not the king, since his statement would then be a lie.

Therefore Lavesh is the king. Hence Manoj is the bureaucrat, and Mayank is the thief.

### #10 - Fireman The Murderer Riddle

Acting on an anonymous phone call, the police raid a house to arrest a suspected murderer. They don't know what he looks like but they know his name is John and that he is inside the house. The police bust in on a carpenter, a lorry driver, a mechanic and a fireman all playing poker. Without hesitation or communication of any kind, they immediately arrest the fireman. How do they know they've got their man?

The fireman is the only man in the room. The rest of the poker players are women.