This edition of Alex’s Monday Puzzle was published on Sunday in error. We regret the error.
Today’s puzzles are about pawns on a chessboard, but they require no expertise at chess. All you need to know is that the queen can move in any direction, for any number of squares.
The first puzzle was devised by Maurice Ashley, the US chess grandmaster, and taken from his app Maurice Ashley Teaches Chess. He describes it as a visualisation exercise to complete in less than two minutes.
Can you find a path in which the queen captures all 11 pawns in exactly 11 moves? (The pawns do not move or protect each other.)
It’s a fun puzzle, a bit harder than you might expect.
The reason it came to my attention, however, is because Maurice’s visualisation exercise caused a flurry of excitement in the hard core puzzle community at StackExchange.
Bernardo Recamán (a friend of this column and legend in recreational maths circles) asked if was possible to keep the constraint of the puzzle but add more pawns.
In other words, how many pawns can you put on a chessboard such that the queen has a unique path to capture all the pawns in precisely as many moves as there are pawns.
Daniel Mathias found an example with 14 pawns.
Not to be outdone, loopy walt upped it to 16 pawns
Before posting one with 19 pawns.
Can you solve them all?
If you are trying the puzzles out on a screen, it is helpful to use an app like Markup, but if you are old school and prefer pen and paper, I have put them all on a pdf here.
I’ll be back at 5pm UK with the solutions.
NO SPOILERS Please discuss your favourite chess grandmasters.
Thanks to Bernardo Recamán.
I set a puzzle here every two weeks on a Monday. I’m always on the look-out for great puzzles. If you would like to suggest one, email me.
I give school talks about maths and puzzles (online and in person). If your school is interested please get in touch.
