The retrograde evaluation of a recreation is the evaluation of what occurred with a view to attain a specific state of play. There’s a big literature about this form of downside in chess.


At present’s first puzzle is retrograde evaluation of snakes and ladders.

1. Model new it’s retro

Three younger kids, Crimson, Inexperienced, and Blue are enjoying snakes and ladders. They’re referred to as away, leaving the board, together with the die, as under. The die is displaying the final quantity rolled.


Deduce whose flip it now’s, and the order of play.

Snakes and Ladders - Puzzle

Some clarifications in regards to the guidelines of snakes and ladders that the children are enjoying.

  • The sport begins with every participant placing their marker on 1.

  • Every participant roles a single die. In the event you roll a 6, you get an additional throw.

  • The gamers take turns in a hard and fast order.

  • You go up ladders, and down snakes. It’s attainable to go up two ladders, or down two snakes, or up a ladder and down a snake on the identical flip.

  • The winner is the participant who lands precisely on 100. (If you’re on 98 and roll a 3, you ‘bounce again’ and land on 99.)

  • If a participant lands on a sq. occupied by one other participant, the participant is not despatched again to sq. 1.

I’ll offer you one trace: the sport that was performed was relatively excessive – a number of 6s have been rolled!

The snakes and ladders puzzle was created by Ammar Fathin Sabili, an Indonesian who’s learning for a PhD in pc science on the Nationwide College of Singapore.

He additionally composed the next puzzle:

2. The lacking image

What image would match completely within the centre of this brand?

Symbol puzzle
Illustration: Ammar Fathin Sabili

Every of the statements describes the image neatly. (One of many statements requires data of mathematical notation, however the different three don’t.)

I’ll be again at 5pm UK with the solutions to each puzzles. In the meantime, NO SPOILERS.

As a substitute focus on board video games.

UPDATE: The options will be learn right here.

I set a puzzle right here each two weeks on a Monday. I’m at all times on the look-out for excellent puzzles. If you want to recommend one, e-mail me.

I give college talks about maths and puzzles (on-line and in individual). In case your college is please get in contact.

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