Brain Teasers the Mind Sharpeners - Brain Teasers Page 2

Brain Teasers the Mind Sharpeners

No.1	A boat has a ladder that has six rungs. Each rung is one foot apart. The bottom rung is one foot from the water. The tide rises at 12 inches every 15 minutes. High tide peaks in one hour. When the tide is at its highest, how many rungs are under water?	Solution None. The boat is floating on the water, so as the tide rises, so does the ladder.
No.2	You have a lighter and two fuses that take exactly one hour to burn, but they don't burn at a steady rate. For example, one fuse could take 59 minutes to burn the first inch and then burn the rest of the fuse in the last minute. How would you use these two fuses to measure 45 minutes?	Solution Light the first fuse on both ends and the second fuse at only one end. When the first fuse burns out you know 30 minutes have passed. Light the other end of the second fuse and when it burns out, 45 minutes have passed.
No.3	You have two buckets - one holds exactly 5 gallons and the other 3 gallons. How can you measure 4 gallons of water into the 5 gallon bucket? (Assume you have an unlimited supply of water and that there are no measurement markings of any kind on the buckets.)	Solution 1. Fill the 3-gallon bucket. 2. Pour the 3 gallons of water into the 5-gallon bucket 3. Fill the 3-gallon bucket again. 4. Fill up the 5-gallon bucket with the 3-gallon bucket, leaving you with 1 gallon left in the 3-gallon bucket. 5. Empty out the 5-gallon bucket. 6. Pour the remaining 1 gallon of water from the 3-gallon bucket into the 5-gallon bucket. 7. Fill the 3-gallon bucket. 8. Pour the 3 gallons of water from the 3-gallon bucket into the 5-gallon bucket leaving you with 4 gallons of water in the 5-gallon bucket.
No.4	During WWII, there was a bridge connecting Germany and Switzerland, and on the German side, there was a sentry tower with a guard in it. He would come out every three minutes to check on the bridge, and he had orders to turn back anyone who tried to get into Germany, and shoot anyone trying to escape without a pass. There was a woman who desperately needed to get into Switzerland, and she knew she didn't have time to get a pass. It would take her at least six minutes to cross the bridge, but she managed to do it. How?	Solution She walked on the bridge towards Switzerland for 3 minutes and just as the guard was about to come out, she turned around walking back to Germany. The guard saw her and asked for her pass but she didn't have one and was sent back (or what the guard thought was back) to Switzerland. In her case it was the very country she wanted to go to.
No.5	A man can make perfect counterfeit bills. They look exactly like real ones, they're made of exactly the same materials, made the same way, everything. So perfect, one could pretty much call them real bills. One day he successfully makes a perfect copy of another bill. However, he gets caught when he tries to use the copy. How is this possible?	Solution He made a perfect copy of a counterfeit bill.
No.6	A prisoner is told "If you tell a lie we will hang you; if you tell the truth we will shoot you." What can he say to save himself?	Solution You will hang me.
No.7	How many people can read hex if only you and dead people can read hex?	Solution The trick is that the word dead represents a number in hexadecimal. That number in base 10, plus one to include yourself, is: 57005 + 1 = 57006.
No.8	A man is traveling with a fox and two chickens, if he leaves the fox alone with the chickens the fox will eat the chickens. He comes to a river and needs to cross it, he finds a small boat that can carry only him and one animal, how does he get himself, the fox and two chickens across the river safely?	Solution Take the fox over, return with nothing. Go over with one chicken, return with the fox. Go over with the second chicken, return with nothing. Finally, take the fox over.
No.9	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?	Solution The man in the picture is his son. Since he doesn't have any brothers or sisters, the statement my father's son is himself. A shortened version would be this man's father is myself, so he is the father of the man in the picture.
No.10	A man and his son had a terrible car accident and were rushed to the hospital. The man died on the way, but the son was still alive and a surgeon was called in to operate. However, the surgeon saw the young boy and said, "I can't operate on this boy. He's my son." How is this possible?	Solution The surgeon was his mother.
No.11	A wise king devised a contest to see who would receive the Princess' hand in marriage. The Princess was put in a 50x50 foot carpeted room. Each of her four suitors were put in one corner of the room with a small box to stand on. The first one to touch the Princess hand would be the winner and become the new King.	Solution Asked the princess to touch his hand.
No.12	The rules of the test were that the contestants could not walk over the carpet, cross the plane of the carpet, or hang from anything; nor could they use anything but their body and wits (i.e. no magic or telepathy, nor any items such as ladders, block and tackles etc). One suitor figured out a way and married the Princess and became the new King. What did he do?	Solution Asked the princess to touch his hand.
No.13	Two guards were on duty outside a barracks. One faced up the road to watch for anyone approaching from the North. The other looked down the road to see if anyone approached from the South. Suddenly one of them said to the other, "Why are you smiling?" How did he know his companion was smiling?	Solution They were facing each other. As to why his companion was smiling, the world may never know.
No.14	You're riding a horse. To the right of you is a cliff and in front of you is an elephant going the same pace as you and you can't overtake it. To the left of you is a hippo running at the same speed and behind you is a lion chasing you. How do you get to safety?	Solution Get off the merry-go-round.
No.15	You have 50 quarters on the table in front of you. You are blindfolded and cannot discern whether a coin is heads up or tails up by feeling it. You are told that x coins are heads up, where 0 < x < 50. You are asked to separate the coins into two piles in such a way that the number of heads up coins in both piles is the same at the end. You may flip any coin over as many times as you want. How will you do it?	Solution Take x coins, flip all of them and put them in one pile. The rest of the coins form the second pile.
No.16	You have four chains. Each chain has three links in it. Although it is difficult to cut the links, you wish to make a single loop with all 12 links. What is the fewest number of cuts you must make to accomplish this task?	Solution 3 cuts. Cut each link in one chain. Separate them, and use the links to join the ends of the 3 intact chains.
No.17	Three closed boxes have either white marbles, black marbles or both, and they are labeled white, black and both. However, you're told that each of the labels are wrong. You may reach into one of the boxes and pull out only one marble. Which box should you remove a marble from to determine the contents of all three boxes?	Solution The one labeled both. Since you know it's labeled incorrectly, it must have all black marbles or all white marbles. After you determine what it contains, you can identify the other two boxes by the process of elimination.
No.18	A glass of water with a single ice cube sits on a table. When the ice has completely melted, will the level of the water have increased, decreased or remain unchanged?	Solution Remain unchanged. When frozen, the ice cube displaces its weight.
No.19	You are given eight coins and told that one of them is counterfeit. The counterfeit one is slightly heavier than the other seven. Otherwise, the coins look identical. Using a simple balance scale, can you determine which coin is counterfeit using the scale only twice?	Solution First weigh three coins against three others. If the weights are equal, weigh the remaining two against each other. The heavier one is the counterfeit. If one of the groups of three is heavier, weigh two of those coins against each other. If one is heavier, it's the counterfeit. If they have equal weight, the third coin is the counterfeit.
No.20	I was visiting a friend one evening and remembered that he had three daughters. I asked him how old they were. "The product of their ages is 72," he answered. Quizzically, I asked, "Is there anything else you can tell me?" "Yes," he replied, "the sum of their ages is equal to the number of my house." I stepped outside to see what the house number was. Upon returning inside, I said to my host, "I'm sorry, but I still can't figure out their ages." He responded apologetically, "I'm sorry, I forgot to mention that my oldest daughter likes strawberry shortcake." With this information, I was able to determine all of their ages. How old is each daughter? You have enough information to solve the puzzle.	Solution 3, 3, and 8. The only groups of 3 factors of 72 to have non-unique sums are 2, 6, 6 and 3, 3, 8 (both add up to 14). The presence of a single oldest child eliminates 2,6,6.
No.21	You're in a room with two doors. There's a guard at each door. One door is the exit, but behind the other door is something that will kill you. You're told that one guard always tells the truth and the other guard always lies. You don't know which guard is which. You are allowed to ask one question to either of the guards to determine which door is the exit. What question should you ask?	Solution Ask either guard what door the other guard would say is the exit, then choose the opposite door. If you ask the guard who always tells the truth, he knows the other guard would lie, so he'll point you to the door leading to death. If you ask the guard who always lies, he knows the other guard would truthfully show you the exit, so he'll lie and point you to the door leading to death.
No.22	How far can a dog run into the forest?	Solution Halfway. After that it will be running out of the forest.
No.23	If eggs are 12¢ a dozen, how much would it cost for 100 eggs?	Solution $1. If eggs are 12¢ a dozen, each egg costs 1¢, so 100 eggs would be 100¢, or $1.
No.24	You are a prisoner sentenced to death. The Emperor offers you a chance to live by playing a simple game. He gives you 50 black marbles, 50 white marbles and 2 empty bowls. He then says, "Divide these 100 marbles into these 2 bowls. You can divide them any way you like as long as you use all the marbles. Then I will blindfold you and mix the bowls around. You can then choose one bowl and remove one marble. If the marble is white, you live, but if the marble is black...you die. How do you divide the marbles up so that you have the greatest probability of choosing a white marble?	Solution Place 1 white marble in one bowl, and place the rest of the marbles in the other bowl (49 whites, and 50 blacks). This way you begin with a 50/50 chance of choosing the bowl with just one white marble and living. But even if you choose the other bowl, you still have an almost 50% chance of picking one of the 49 white marbles. There are no guarantees in life, but this is your best bet at surviving.
No.25		Solution TEXTDISPLAY