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Opposite you see a grid containing six boxes and a grid containing five boxes. Try to draw a line which crosses each line segment of the first grid, but without crossing over your own line. Moreover, you may cross each line segment only once. The third drawing shows an example of the method. Apparently, the five-box grid (and any uneven grid) has never been solved and is considered impossible. But you can always try, maybe you get lucky! To go to the Java version of this puzzle Click here |
Move two buttons to get two rows (in any direction) of four buttons.
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2+2=4 |
A teacher explains to his class the curious fact that 2 times 2 gives the same answer as 2 plus 2. Although 2 is the only number with this characteristic, there are many pairs of different numbers which can be substituted for A and B in the equation opposite. Can you find such a pair? You may use fractions, but their product must be the same as their sum. |
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The town of Four Oaks owes its name to the fact that one of its founders, who owned a large piece of land, left this land to his four sons on the express condition that they "would divide it into four equal pieces, taking into account the four oaks which had always served as a landmark". The four sons could not work out how to divide the land. Can you divide the land into four equal areas, each containing a tree? |
This innocent-looking problem in mechanics is so difficult that - it is said - Lewis Carroll was perplexed by it.
A cable hangs over a frictionless pulley. Now a weight which exactly balances the monkey hanging on the other side is attached to a massless cable.
A rubber ball falls from the Leaning Tower of Pisa (height 53.70 metres). Every time the ball hits the ground, it bounces back up one-tenth of the length of its fall. What distance does the ball cover before it comes to rest on the ground?
It takes a cyclist three minutes to cover one kilometre with the wind in his back, and it takes him one minute longer to complete the return journey. Assuming he always exerts the same force on the pedals, how long will it take him to cycle one kilometre when there is no wind?
On their way to school, two children who had trouble with the days of the week stopped to sort things out. Lisa said: "If the day after tomorrow is yesterday, then "today" is as far from Saturday as the day which was "today" when the day before yesterday was tomorrow!" On what day of the week did this puzzling conversation take place?
A prison is getting overcrowded and there just isn't any more room to hold new
prisoners. Some of the prisoners are going to have to be let free. The
warden decides, though, that the prisoners are going to have to "earn" their
freedom. One by one the prisoners are led into a room with 2 doors.
The warden proceeds to tell each prisoner "One of those doors is
the door to freedom, while the
other leads to death. In front of the doors are 2 guards. One guard will
only lie, while the other will only tell the truth. I won't reveal who does what.
You may ask one question and one question only, and it may not be a two-part
question. You may ask either guard (Door A or Door B)."
What question could you ask that would assure you the right choice of door?
A hole is made in a sphere passing through its center. Imagine that the removed part is formed by two opposite spherical bowls
with a cylinder between them. The question is:
Knowing the length of the cylinder is 6cm, what is the residual volume of the sphere?
Snaking Lines
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