perplexus.info :: Just Math : Find that decade

Find that decade (Posted on 2014-01-06)

There has been only a single instance in the course of American history (1776 AD onwards) wherein there was a decade in which four of the years were prime numbers. Find that decade.

See The Solution Submitted by K Sengupta

Rating: 5.0000 (1 votes)

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1879 , 1877, 1873, 1871 --were prime years.*

*btw ,exactly twenty years LATER 1891, 1893, 1895, 1897, 1899, were ALL composite!!

(it will happen again in 2081, 2083 ,2087, 2089),+

exactly twenty years LATER 2101,2103,2105,2107 &2109 will be ALL composite!!

Edited on January 7, 2014, 8:54 am

Posted by Ady TZIDON on 2014-01-06 10:18:21

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