# Happy New Year!

So, the Elfnigma (PuzzleSolution) that was set as Day 9 of the Mathematical Advent Calendar suggests some further chess board related puzzles featuring other varieties of faerie folk. Obviously, the elves of the puzzle were based on queens from a chessboard, but while queens can take any piece in the same row, column or diagonal, elves could only see tiles in these directions that were either adjacent (diagonally, horizontally or vertically) or of the same colour.

The question asked was (essentially) how many elves could be placed on a chess board, such that none could see any other (just as the Eight Queens Problem asks how eight queens can be placed on a chess board such that none threatens any other). This leads naturally to other questions involving magical creatures that are based on other chess pieces. Continue reading

# The Indisputable Santa Mathematical Advent CalendarDay 9

Happy 9th of December!

Throughout the month, to accompany the release of our book on the Mathematics of ChristmasHannah Fry & I are tweeting out Christmathsy bits and pieces, one a day, advent calendar style. Assuming we don’t run out of ideas, that is…

[EDIT: Two variants of this puzzle can be found HERE.]

Today, a tougher puzzle. We’ll give you the whole weekend to work it out. Solution on Monday…