It is observed that January 1, 2002 was the first "sum-day" of the 21st century, that is, when that date is written in the mm-dd-yy format, it becomes 01/01/02, and 1+1 = 2. More specifically, a "sum-day" is a date in which the month and the day add up to the year.

(i) Determine the total number of sum-days from January 1, 2002 to December 31, 2100 inclusively.

(ii) Determine the last sum-day in the period covered under (i).

The number of  dates qualifying as a "sum day" within  the period   2002-2043 and  the  number of days in a year is clearly the same number. 

 365  is the answer, since a triplet 2-29-31 does not exist.

To double- check , I juSt counted the dates by year:

2002-1,2003-2,.. 2013-12,...  2023-10,...2043-1,...2038-6, ....2044-0 ....2099-0,2100-0 .

 

 

Edited on January 14, 2010, 10:10 pm

Posted by Ady TZIDON on 2010-01-14 19:26:43