Knowledge Puzzle

John and Jacob are on the two opposite banks of a river. They both have a rowing boat.
They both start at the same time towards the opposite bank. They pass each other at 180 meters from the bank where john departed. When reaching the opposite bank, they both take a rest for the same amount of time before they return. On the way back, they pass each other at 100 meters from the bank from where John returned.
John and Jacob both row with a constant speed, but Jacob rows faster.
How wide is the river?
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Peasant John wants to buy new chickens, pigs, and horses. A new chicken costs 50 euro cents, a pig 3 euros, and a horse 10 euros. Peasant John has 100 euros with which he wants to buy exactly 100 animals, but in such a way, that she has at least one of each kind of animal.
How many animals must peasant John buy of each kind?
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A boy leaves home in the morning to go to school. At the moment that he leaves the house, he looks at the clock in the mirror. The clock has no number indication and for this reason, the boy makes a mistake in interpreting the time (mirror image). Just assuming the clock must be out of order, the boy cycles to school, where he arrives after twenty minutes. At that moment, the clock at school shows a time that is two and a half hours later than the time that the boy saw on the clock at home.
At what time did he reach school?
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Consider a list of 2000 statements:
1) Exactly one statement on this list is false.
2) Exactly two statements on this list are false.
3) Exactly three statements on this list are false.
. . .
2000) Exactly 2000 statements on this list are false.
Which statements are true and which are false?What happens if you replace “exactly” with “at least”?
What happens if you replace “exactly” with “at most”?
What happens in all three cases if you replace “false” with “true”?
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There is a car with a flat roof, on a plain level road. There is a helium balloon in the car, barely scraping the roof – any slight force will move it. You start the car and accelerate forward very fast. Does the balloon move with respect to the car? If so, how ? (No any trick and no any air from window)
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There are two cylindrical rods of iron, identical in size and shape. One is a permanent magnet. The other is just nonmagnetised iron — attractable by magnets, but not permanently magnetic itself. Without any instrument, how can you determine which is Magnetic ?
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A boat of mass M1 is floating in a lake of water. The volume of the lake is V. The water surface is initially at height h, as measured relative to the lake’s floor. There is an anchor of mass M2 sitting on the boat’s deck. A person standing on deck picks up the anchor and throws it overboard. The anchor then sinks to the bottom of the lake, and the water surface height becomes h’.
Which of the following qualitative relationships is correct? What assumptions are you making about the values of M1, M2, h, and V?
h’ h
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