NRICH Solution to Weekly Problem 13

Solution:

Weekly Problem 13 - 2013

Stage: 2 and 3 

2013 is the only year before 2015 in which each date will fall on the same day of the week as it did in 2002.

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Year	2002	2003	2004	2005	2006	2007	2008
1st January	Tue	Wed	Thu	Sat	Sun	Mon	Tue
	2009	2010	2011	2012	2013	2014	2015
	Thu	Fri	Sat	Sun	Tue	Wed	Thu

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So two of the years before 2015 start on a Tuesday. But each date has to fall on the same day and since 2008 is a leap year but 2002 wasn't, it must be excluded.