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Topic: A Decade And Year Puzzle (Read 387 times) |
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K Sengupta
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A Decade And Year Puzzle
« on: Feb 19th, 2006, 10:52pm » |
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Determine the year ( in YYYY format ) belonging to a certain decade inthe 21st Century such that none of the years in the said decade isdivisible by 13 and the year under reference constitutes the only prime number in the said decade. What 4-digit year is the only prime number in its decade, such that this decade is in the 20th Century and contains no numbers divisible by 13?
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Three Hands
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Re: A Decade And Year Puzzle
« Reply #1 on: Feb 20th, 2006, 7:38am » |
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Decades that fit the non-divisible by 13 requirement: 2030s, 2070s. Primes that fall within those decades: 2039. For the second problem, decades that fit non-divisibility by 13 requirement: 1900s, 1940s, 1990s. Primes that fall within those decades: 1901, 1907, 1949, 1993, 1997, 1999 OK, I'll admit, I got someone else to work out the primes for me...
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