Elf Chalkboard Puzzle

This is a repost promoting content originally published elsewhere. See more things Dan's reposted.

I write the integers 1-9999 (inclusive) on a huge chalkboard. Each number is written once.

During the night the board is visited by a series of naughty math elves (it’s a thing!)

Each elf approaches the board, selects two numbers at random, erases them, and replaces them with a new number that is the absolute difference of the two numbers erased.

This vandalism continues all night until there is just one number remaining.

I return to the board the next morning and find the single number of the board. The question is: Is this remaining number odd or even?

Elf Chalkboard

A fun, lightweight maths puzzle for your amusement. I was able to find the right answer pretty quickly by spotting the pattern; it took me longer to find the words to adequately explain the pattern.

0 comments

    Reply here

    Your email address will not be published. Required fields are marked *

    Reply on your own site

    Reply by email

    I'd love to hear what you think. Send an email to b15423@danq.me; be sure to let me know if you're happy for your comment to appear on the Web!