Two circles caused headaches during an entrance test in the USA.
It looks so easy.
Can you come up with the right solution?
Did you pay attention at school?
This math puzzle will challenge your brain cells.
Because, as is so often the case, the first thought is not always the right one.
Here we go!
Riddle: How often does the small circle revolve around the large one?
A small circle rolls once completely around a large circle.
Both circles touch each other.
The radius of the large circle is
three times the size of the small one
.
How often does the small circle turn around itself?
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+
In 1982, thousands of university applicants in the USA failed because of this math puzzle.
© fkn
That’s the solution
The correct solution is:
four times
.
The radius of the great circle is three times as large, so so is its circumference.
For a straight stretch, three times would be the correct answer.
However, the curvature
adds
an
additional turn
.
The reason: the center of the small circle has to cover a larger circular path when it goes around the large circle, namely the radius of the large circle plus its own radius.
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Prospective students failed the university test
This phenomenon is also called the
coin rotation paradox
in mathematics
and was part of an entrance examination for students in the USA in 1982.
At that time
, none of the participants were able to solve the problem correctly
because the multiple choice test simply lacked the correct answer among the possible answers.
When three students finally protested, 300,000 tests had to be re-graded.
(as) * Merkur.de is an offer from IPPEN.MEDIA
.
To continue the puzzle:
astronauts have
to pass
this dice test - do you know
the answer
?
Source: NewYorkTimes, mindyourdecisions.com
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