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1996 - Back to the Number Puzzles Using the numerals 1, 9, 9 and 6, mathematical symbols +, -, x, :, root and brackets create the following numbers: 29, 32, 35, 38, 70, 73, 76, 77, 100 and 1000. All the numerals must be used in the given order (each just once) and without turning upside down. This old topic is locked since it was answered many times. You can check solution in the Spoiler below. Pls visit New Puzzles section to see always fresh brain teasers.

100 - Back to the Number Puzzles Using four sevens (7) and a one (1) create the number 100. Except the five numerals you can use the usual mathematical operations (+, -, x, , root and brackets (). This old topic is locked since it was answered many times. You can check solution in the Spoiler below. Pls visit New Puzzles section to see always fresh brain teasers.

Equation - Back to the Number Puzzles Rectify the following equality 101 - 102 = 1 by moving just one digit. This old topic is locked since it was answered many times. You can check solution in the Spoiler below. Pls visit New Puzzles section to see always fresh brain teasers.

Number Sequences - Back to the Number Puzzles There are infinite formulas that will fit any finite series. Try to guess the following number in each sequence (using the most simple mathematical operations, because as I mentioned, there is more than one solution for each number sequence). * 8723, 3872, 2387, ? * 1, 4, 9, 18, 35, ? * 23, 45, 89, 177, ? * 7, 5, 8, 4, 9, 3, ? * 11, 19, 14, 22, 17, 25, ? * 3, 8, 15, 24, 35, ? * 2, 4, 5, 10, 12, 24, 27, ? * 1, 3, 4, 7, 11, 18, ? * 99, 92, 86, 81, 77, ? * 0, 4, 2, 6, 4, 8, ? * 1, 2, 2, 4, 8, 11, 33, ? * 1, 2, 6, 24, 120, ? * 1, 2, 3, 6, 11, 20, 37, ? * 5, 7, 12, 19, 31, 50, ? * 27, 82, 41, 124, 62, 31, 94, 47, 142, 71, 214, 107, ? * 126, 63, 190, 95, 286, 143, 430, 215, 646, 323, 970, ? * 4, 7, 15, 29, 59, 117, ? * 2, 3, 2, 3, 2, 4, 2, 3, 2, 3, 2, 5, 2, 3, 2, 3, 2, 4, 2, 3, 2, 3, 2, 5, 2, 3, 2, 3, 2, 4, 2, 3, 2, 3, 2, 5, ? * 4, 4, 341, 6, 4, 4, 6, 6, 4, 4, 6, 10, 4, 4, 14, 6, 4, 4, 6, 6, 4, 4, 6, 22, 4, 4, 9, 6, ? This old topic is locked since it was answered many times. You can check solution in the Spoiler below. Pls visit New Puzzles section to see always fresh brain teasers.

Bear - Back to the Einstein's Riddles The famous physicist allegedly made this riddle for his scholars. A fellow encountered a bear in a wasteland. There was nobody else there. Both were frightened and ran away. Fellow to the north, bear to the west. Suddenly the fellow stopped, aimed his gun to the south and shot the bear. What colour was the bear? If you don't know, this may help you: if the bear ran about 3.14 times faster than the fellow (still westwards), the fellow could have shot straight in front of him, however for the booty he would have to go to the south. This old topic is locked since it was answered many times. You can check solution in the Spoiler below. Pls visit New Puzzles section to see always fresh brain teasers.

Neighbors - Back to the Einstein's Riddles It is said that this quiz was made up by Albert Einstein and according to him 98% will not solve it. There is a row of five houses, each having a different color. In these houses live five people of various nationalities. Each of them nurtures a different beast, likes different drinks and smokes different brand of cigars. 1. The Brit lives in the Red house. 2. The Swede keeps dogs as pets. 3. The Dane drinks tea. 4. The Green house is on the left of the White house. 5. The owner of the Green house drinks coffee. 6. The person who smokes Pall Mall rears birds. 7. The owner of the Yellow house smokes Dunhill. 8. The man living in the center house drinks milk. 9. The Norwegian lives in the first house. 10. The man who smokes Blends lives next to the one who keeps cats. 11. The man who keeps horses lives next to the man who smokes Dunhill. 12. The man who smokes Blue Master drinks beer. 13. The German smokes Prince. 14. The Norwegian lives next to the Blue house. 15. The man who smokes Blends has a neighbor who drinks water. Which of the five house owners keeps fish as a pet? (are you one of the 2%). This old topic is locked since it was answered many times. You can check solution in the Spoiler below. Pls visit New Puzzles section to see always fresh brain teasers.

Meeting (meet this challenge) - Back to the Einstein's Riddles Another hard nut to crack (just like Einstein's) was published in the QUIZ 11/1986. Eight married couples meet to lend one another some books. Couples have the same surname, employment and car. Each couple has a favourite colour. Furthermore we know the following facts: 1. Daniella Black and her husband work as Shop-Assistants. 2. The book "The Seadog" was brought by a couple who drive a Fiat and love the colour red. 3. Owen and his wife Victoria like the colour brown. 4. Stan Horricks and his wife Hannah like the colour white. 5. Jenny Smith and her husband work as Warehouse Managers and they drive a Wartburg. 6. Monica and her husband Alexander borrowed the book "Grandfather Joseph". 7. Mathew and his wife like the colour pink and brought the book "Mulatka Gabriela". 8. Irene and her husband Oto work as Accountants. 9. The book "We Were Five" was borrowed by a couple driving a Trabant. 10. The Cermaks are both Ticket-Collectors who brought the book "Shed Stoat". 11. Mr and Mrs Kuril are both Doctors who borrowed the book "Slovacko Judge". 12. Paul and his wife like the colour green. 13. Veronica Dvorak and her husband like the colour blue. 14. Rick and his wife brought the book "Slovacko Judge" and they drive a Ziguli. 15. One couple brought the book "Dame Commissar" and borrowed the book "Mulatka Gabriela". 16. The couple who drive a Dacia, love the colour violet. 17. The couple who work as Teachers borrowed the book "Dame Commissar". 18. The couple who work as Agriculturalists drive a Moskvic. 19. Pamela and her husband drive a Renault and brought the book "Grandfather Joseph". 20. Pamela and her husband borrowed the book that Mr and Mrs Zajac brought. 21. Robert and his wife like the colour yellow and borrowed the book "The Modern Comedy". 22. Mr and Mrs Swain work as Shoppers. 23. "The Modern Comedy" was brought by a couple driving a Skoda. Is it a problem to find out everything about everyone from this information? This old topic is locked since it was answered many times. You can check solution in the Spoiler below. Pls visit New Puzzles section to see always fresh brain teasers.

Ships - Back to the Einstein's Riddles There are 5 ships in a port. 1. The Greek ship leaves at six and carries coffee. 2. The ship in the middle has a black chimney. 3. The English ship leaves at nine. 4. The French ship with a blue chimney is to the left of a ship that carries coffee. 5. To the right of the ship carrying cocoa is a ship going to Marseille. 6. The Brazilian ship is heading for Manila. 7. Next to the ship carrying rice is a ship with a green chimney. 8. A ship going to Genoa leaves at five. 9. The Spanish ship leaves at seven and is to the right of the ship going to Marseille. 10. The ship with a red chimney goes to Hamburg. 11. Next to the ship leaving at seven is a ship with a white chimney. 12. The ship on the border carries corn. 13. The ship with a black chimney leaves at eight. 14. The ship carrying corn is anchored next to the ship carrying rice. 15. The ship to Hamburg leaves at six. Which ship goes to Port Said? Which ship carries tea? This old topic is locked since it was answered many times. You can check solution in the Spoiler below. Pls visit New Puzzles section to see always fresh brain teasers.

Gardens - Back to the Einstein's Riddles Five friends have their gardens next to one another, where they grow three kinds of crops: fruits (apple, pear, nut, cherry), vegetables (carrot, parsley, gourd, onion) and flowers (aster, rose, tulip, lily). 1. They grow 12 different varieties. 2. Everybody grows exactly 4 different varieties 3. Each variety is at least in one garden. 4. Only one variety is in 4 gardens. 5. Only in one garden are all 3 kinds of crops. 6. Only in one garden are all 4 varieties of one kind of crops. 7. Pears are only in the two border gardens. 8. Paul's garden is in the middle with no lily. 9. Aster grower doesn't grow vegetables. 10. Rose grower doesn't grow parsley. 11. Nuts grower has also gourd and parsley. 12. In the first garden are apples and cherries. 13. Only in two gardens are cherries. 14. Sam has onions and cherries. 15. Luke grows exactly two kinds of fruit. 16. Tulips are only in two gardens. 17. Apples are in a single garden. 18. Only in one garden next to the Zick's is parsley. 19. Sam's garden is not on the border. 20. Hank grows neither vegetables nor asters. 21. Paul has exactly three kinds of vegetable. Who has which garden and what is grown where? This old topic is locked since it was answered many times. You can check solution in the Spoiler below. Pls visit New Puzzles section to see always fresh brain teasers.

Pouring water I. - Back to the Water and Weighing Puzzles If you had a 5-liter bowl and a 3-liter bowl, and an unlimited access to water, how would you measure exactly 4 liters? This old topic is locked since it was answered many times. You can check solution in the Spoiler below. Pls visit New Puzzles section to see always fresh brain teasers.

Pouring water II. - Back to the Water and Weighing Puzzles Given three bowls: 8, 5 and 3 liters capacity, divide 8 liters in half (4 + 4 liters) with the minimum number of water transfers. Note that the 8-liter bowl is initially filled with 8 liters of water and the other two bowls are empty - that is all water you have. This old topic is locked since it was answered many times. You can check solution in the Spoiler below. Pls visit New Puzzles section to see always fresh brain teasers.

Pouring water III. - Back to the Water and Weighing Puzzles Given three bowls: 7, 4 and 3 liters capacity. Only the 7-liter is full. Pouring the water the fewest number of times, make the quantities of 2, 2, and 3 liters. This old topic is locked since it was answered many times. You can check solution in the Spoiler below. Pls visit New Puzzles section to see always fresh brain teasers.

Pouring water IV. - Back to the Water and Weighing Puzzles How can you measure 6 liters of water using only 4 and 9-liter bowls? This old topic is locked since it was answered many times. You can check solution in the Spoiler below. Pls visit New Puzzles section to see always fresh brain teasers.

Pouring water V. - Back to the Water and Weighing Puzzles Measure exactly 2 liters of water if you have: 1. 4 and 5-liter bowls 2. 4 and 3-liter bowls This old topic is locked since it was answered many times. You can check solution in the Spoiler below. Pls visit New Puzzles section to see always fresh brain teasers.

Pouring water VI. - Back to the Water and Weighing Puzzles Given three bowls: bowl A (8 liters capacity) filled with 5 liters of water; bowl B (5 liters capacity) filled with 3 liters of water; and bowl C (3 liters capacity) filled with 2 liters of water. Can you measure exactly 1 liter, by transferring the water only 2 times? This old topic is locked since it was answered many times. You can check solution in the Spoiler below. Pls visit New Puzzles section to see always fresh brain teasers.

Weighing I. - Back to the Water and Weighing Puzzles You have 10 bags with 1000 coins each. In one of the bags, all coins are forgeries. A true coin weighs 1 gram; each counterfeit coin weighs 1.1 gram. If you have an accurate scale, which you can use only once, how can you identify the bag with the forgeries? And what if you didn't know how many bags contained counterfeit coins? This old topic is locked since it was answered many times. You can check solution in the Spoiler below. Pls visit New Puzzles section to see always fresh brain teasers.

Weighing II. - Back to the Water and Weighing Puzzles A genuine gummy drop bear has a mass of 10 grams, while an imitation gummy drop bear has a mass of 9 grams. Spike has 7 cartons of gummy drop bears, 4 of which contain real gummy drop bears and the others – imitation. Using a scale only once and the minimum number of gummy drop bears, how can Spike determine which cartons contain real gummy drop bears? This old topic is locked since it was answered many times. You can check solution in the Spoiler below. Pls visit New Puzzles section to see always fresh brain teasers.

Weighing III. - Back to the Water and Weighing Puzzles This puzzle goes a step further from the previous one. You have eight bags, each of them containing 48 coins. Five of those bags contain only true coins, the rest of them contain fake coins. A fake coin weighs 1 gram less than a real coin. You have an accurate scale, with the precision of up to 1 gram. Weighing only once and using the minimum number of coins, how can you find the bags containing the fake coins? This old topic is locked since it was answered many times. You can check solution in the Spoiler below. Pls visit New Puzzles section to see always fresh brain teasers.

Weighing IV. - Back to the Water and Weighing Puzzles One of twelve tennis balls is a bit lighter or heavier (you do not know which) than the others. How would you identify this odd ball if you could use an old two-pan balance scale only 3 times? You can only balance one set of balls against another, so no reference weights and no weight measurements. This old topic is locked since it was answered many times. You can check solution in the Spoiler below. Pls visit New Puzzles section to see always fresh brain teasers.

Weighing V. - Back to the Water and Weighing Puzzles On a Christmas tree there were two blue, two red, and two white balls. All seemed same. However, in each color pair, one ball was heavier. All three lighter balls weighed the same, just like all three heavier balls. Using a balance scale twice, identify the lighter balls. This old topic is locked since it was answered many times. You can check solution in the Spoiler below. Pls visit New Puzzles section to see always fresh brain teasers.

Weighing VI. - Back to the Water and Weighing Puzzles There are 9 similar balls. Eight of them weigh the same and the ninth is a bit heavier. How would you identify the heavier ball if you could use a two-pan balance scale only twice? This old topic is locked since it was answered many times. You can check solution in the Spoiler below. Pls visit New Puzzles section to see always fresh brain teasers.

Weighing VII. - Back to the Water and Weighing Puzzles Given 27 table tennis balls, one is heavier than the others. What is the minimum number of weighings (using a two-pan balance scale) needed to guarantee identifying the heavy one? Always. Of course, the other 26 balls weigh the same. This old topic is locked since it was answered many times. You can check solution in the Spoiler below. Pls visit New Puzzles section to see always fresh brain teasers.

Weighing VIII. - Back to the Water and Weighing Puzzles Suppose that the objects to be weighed may range from 1 to 121 pounds at 1-pound intervals: 1, 2, 3,..., 119, 120 and 121. After placing one such weight on either of two weighing pans of a pair of scales, one or more precalibrated weights are then placed in either or both pans until a balance is achieved, thus determining the weight of the object. If the relative positions of the lever, fulcrum, and pans may not be changed, and if one may not add to the initial set of precalibrated weights, what is the minimum number of such weights that would be sufficient to bring into balance any of the 121 possible objects? This old topic is locked since it was answered many times. You can check solution in the Spoiler below. Pls visit New Puzzles section to see always fresh brain teasers.

Hourglass I. - Back to the Water and Weighing Puzzles Having 2 sand-glasses: one 7-minute and the second one 4-minute, how can you correctly time 9 minutes? This old topic is locked since it was answered many times. You can check solution in the Spoiler below. Pls visit New Puzzles section to see always fresh brain teasers.

Hourglass II. - Back to the Water and Weighing Puzzles A teacher of mathematics used an unconventional method to measure a 15-minute time limit for a test. He just used 7 and 11-minutehourglasses. During the whole time he turned sandglasses only 3 times (turning both hourglasses at once count as one flip). Explain how the teacher measured 15 minutes. This old topic is locked since it was answered many times. You can check solution in the Spoiler below. Pls visit New Puzzles section to see always fresh brain teasers.