Jon and Maria are going away for a while. Before they go, they
want know the weight of their bags. First Jon puts his bag on
the scale, which shows 2 kg. Maria puts her on and the scale show
3 kg. When both bags are put simultaneously on the scale it shows
6 kg. Why does it show 6 kg and how much is the real weights of
You are given 9 coins that looks exactly the same. 8 of them are
made in gold and 1 is false. The false coin is lighter then the
others. By using a letter scale, how many tries is the least you
need to find the false coin?
You have ten stacks of identical looking gold coins. Nine of the
stacks contain all real gold coins, and one of the stacks is made
up entirely of fake gold coins. Each real gold coin weighs exactly
1 gram, while each fake gold coin weighs exactly 1.1 grams. Using
a digital scale, how can you determine the stack of fake coins?
RULES: You can only make one measurement. For example, you stack
what you want on the scale, press a button, and get a readout
of the weight. You can do this only once, and once the readout
is displayed it does not change if you remove any coins. You can
mix the coins up in their stacks, separate them, mark them, whatever.
How do you find out for sure which stack contains the fake gold
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Three mathematicians sit around a table and eat pizza. They are
pretty hungry and their table manners are bad. After a while they
look up from the pizza to find that the others have pizza on their
nose, so all of them burst out in laughter. After a while, one
of them stops laughing when he understands that he also has pizza
on his nose. How did he know? (All three are assumed to be good
The baker and the blacksmith
A blacksmith wants to trade a bracelet for bread. He seeks up
the local baker who is interested in the deal. The bracelet has
7 links. And the blacksmith wants to trade 1 link for 1 bread
the following 7 days. The baker thinks it's a shame that he will
receive 7 separate links. After a little thinking, he suggests
another solution which will not require that the bracelet is cut
into 7 pieces. Into how many pieces would you have to cut it?
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Find two integers, both less than 10, which product is 43. (x*y=43)
Measure the water
You have 5 litre and a 3 litre drum. By only using the two drums,
how can you measure 4 litres of water?
Measure the time
You have two hourglasses. One for 8 minutes and one for 5 minutes.
You only have 12 minutes to measure 12 minutes with the two hourglasses.
How do you do?
A wise king is throwing a party in 30 days. He has 1000 bottles
of wine. One bottle is poisoned. The poison isn't detectable and
kills after 29 days. To find out which bottle is poisoned he orders
a minimal group of people to test the wine. How many men does
it take to find the poisoned bottle?
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A family goes to visit relatives in another city for the Christmas.
They travel from 11am to 5pm before they reach their destination.
One week later they travel back exactly the same way and time.
They leave at 11am and are home again at 5pm. Will they ever be
in the same spot at they very same time as on the way there? (With
the exception of that one week passed)
On a meeting, all participants shook hands exactly once. The number
of handshakes was 55. How many participants were there?
True or false
1. At least one of the sentences in this list is false.
2. At least two of the sentences in this list are false.
3. At least three of the sentences in this list are false.
4. At least four of the sentences in this list are false.
5. At least five of the sentences in this list are false.
6. At least six of the sentences in this list are false.
7. At least seven of the sentences in this list are false.
8. At least eight of the sentences in this list are false.
9. At least nine of the sentences in this list are false.
10. At least ten of the sentences in this list are false.
Which of the above sentences are true?
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If half of 5 were 3, what would one-third of 10 be?
Farmer Brown came to town with some watermelons. He sold half
of them plus half a melon, and found that he had one whole melon
left. How many melons did he take to town?
Find two integers, x and y, which holds the following condition
x/y = y.x
Exampe: 4/3 <> 3.4
100 politicians attend a meeting. At least one of them is honest.
If two talk to each other, one of them isn't honest. How many
honest politicians are there at the meeting?
A antique trader bought an item for 7 gold coins, sold it for
8, bought it again for 9 and finally sold it for 10. Did he profit
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Pick a box
A contestant in a famous TV show is asked to point on one of three
boxes. One box contains a prize. The game host will open an empty
box that was not pointed on. After he has opened an empty box,
the contestant is asked to open one of the two remaining unopened
boxes. Which box should the contestant choose in order to have
the biggest probability to win the prize?
The lost man
You are lost in the jungle. Finally you make your way to a well-known
crossing, where one way leads to a tribe where you will be killed
and eaten and the other to a friendly tribe. At the crossing you
find two men. One of them is always lying, while the other is
always talling the truth. It's impossible to know which one of
them who was lying or talking the truth. You can only ask one
of them one question. With what question can you make sure to
come to the friendly tribe?
The warm water tap can fill the bath tub in 8 minutes. The cold
water can fill it in 6 minutes. The drain can empty it in 4 minutes.
Both taps are fully open and so is the drain. Can the tube be
filled? And in that case, how long will it take?