# We Got A Problem #1: 6/5/11

June 5, 2011 2 Comments

Today is June 5, 2011, or 06-05-11 in shorthand (05-06-11 in many countries).

Interestingly, 06 + 05 = 11. How many more times in this century will it happen that the month number plus the day number equal the last two digits of the year number?

*We’d love for readers to be able to explore this problem, so resist the urge to provide answers in the comments. Instead, we’d love helpful suggestions and ideas about different ways to approach the problem, successful or not. If you’d like to provide a full solution, do so with a pingback to your own blog!*

I started with the constraints: What’s the largest number I can make by adding the month and day? What’s the next one, not counting 6/5/11? What’s the smallest?These gave me boundaries. Then I started just figuring them out for each year, looking for patterns and exceptions (no Feb 30, etc.). I ended up making a spreadsheet and counting them up there.

The problem seemed a little daunting at first but once I started defining the edges and filling in some pieces, it wasn’t bad. Like a jigsaw puzzle.

I found a few patterns but there was a lot of brute force involved.

http://sebbamath.wordpress.com/2011/06/08/we-got-a-problem-1/