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Here are my collection of brain teasers that will set you into a thinking mode and sharpen your thinking skill.

Gold bar for hotel payment!

A businessman went to stay in a hotel for seven days. The room rate was one inch gold bar per day. He has a seven-inch gold bar and a special knife that was sharp enough to cut the gold bar into pieces. The hotel insisted that the businessman paid one inch of gold bar at the end of each day and it did not accept advance nor arrears payment. To fulfill this payment scheme, the businessman used his special knife and cut the gold bar twice. He paid the hotel one inch gold bar at the end of each day. How did he achieve this.

[note: this is not a trick question, a perfect solution can be worked out]

Are you a good resource planning manager?

Four men named A, B, C and D, plan to cross a very narrow bridge at night. They have only a torch to share among themselves. They could not cross the bridge together because the bridge could only take at most two men at a time. The speed of crossing for A is 1 minute, B is 2 minutes, C is 5 minutes and D is 10 minutes. Since there is only one torch, someone has to make a return trip to pass the torch to the next group that will be crossing. They have come out with a crossing plan that allows them to cross the bridge in 17 minutes. Can you work out their crossing plan?

[If you can only work out the 19-minute plan, you are only an average resource planner. It is not difficult to work out the 17-minute crossing plan if you think harder]

Finding the odd ball with a balance

There are 12 metallic balls that look exactly the same in appearance. All but one of the balls has a different weight, and that ball can be either heavier or lighter than the remaining 11 balls. Here is the challenge, single out the odd ball using a balance. The rule is you can make use of the balance 3 times only.

[This is a hard problem. Jolly good if you can solve it within 30 minutes]

Three switches for the three light bulbs

In your cellar there are three light switches in the OFF position. Each switch controls 1 of the 3 light bulbs at the top floor. You want to label the switch for each bulb. To do so, an easy way is to switch on one of the switches and go upstairs to see which of the 3 bulbs is lighted. Two trips up the stair and you would be able to label all the three switches. The challenge now is: you can only go upstairs once. How do you do it?

[Think scientifically and you should be able to solve this problem - 15 mins thinking time]

Confusion with basic mathematics & logics!

Three men go to a hotel. The room rate is $30, they each pay $10. Later that night the hotel guy finds out the room is only $25 so he gives $5 to the bellboy to split among the 3 guys. The bellboy did not know how to split the $5 among the 3 men so he kept $2 for himself and gave $1 each to each man.  Think about the mathematics below:

Initially there were $30. The three men paid a total of $27, the bellboy kept $2. It adds up to $29. Where is the missing dollar?

[Test you logic - 2 minutes thinking problem]

Family Problem

A family comprising father, mother, son, daughter, a maid and a dog. They plan to cross a river. There is only one boat available for the crossing and the boat can only take two persons at a time. Only father, mother and the maid know how to row the boat. When father is absent, mother will beat the son. When mother is absent, father will beat the daughter. When the maid is absent, the dog will attack the other members of the family. Suggest a plan so that all of them can cross the river peacefully?

[Resource planning - 15 minutes thinking]

Three Wise Men and their balls!

There were 3 wise men in a kingdom. The king was old and had no son; he had decided to choose a successor among the 3 wise men. One day, he summoned the 3 men to his palace. He took out a bag and said, ' there are 3 white balls and 2 black balls in this bag and now I am going to blindfold all of you and place a ball on top of each of your hats. When I remove your blindfolds, the first who calls out the correct colour of the ball on his own hat shall be the future king. However, the one who guesses it wrong shall be beheaded'. So the king blindfolded the 3 wise men and placed a ball on each of their hats. When he unfold their blindfolds, one of the wise men shouted out 'WHITE' and it was indeed a white ball on his head. How did he know the colour of the ball on his head?

[Logical thinking problem - 10 to 20 minutes thinking time]

Confusing relationship

A son and his father get into a serious car accident.   The boy is taken in one ambulance to a hospital, and the father is taken in another ambulance to a different hospital.  Upon reaching the emergency room, the doctor looks at the boy and says, "I can't work on this patient. He is my son!"   How is this possible?

[An easy problem - need your immediate response in 30 secs]

Rope burning

You have two ropes of different materials and length. However, both ropes take exactly 60 minutes to burn out completely from one end to the other. With these information, are you able to measure exactly 45 minutes ?

Answers

Confusing relationship

[The doctor is the boy's mother]

Finding the odd ball with a balance

Peek at the answer only at your wit's end

Rope burning

(Take one of the ropes and burn it at both ends. At the same time, burn one end of the other rope. When the first rope finishes burning, light the other end of the remaining rope. When it burns out, that's 45 minutes)