The day is finally here: issue 11 is out now! To help you celebrate launch day in style, we’ve set a puzzle hunt: throughout the day, we are posting a series of puzzles. The answers to these puzzles form clues to the four-digit code for the door to let you into the Chalkdust issue 11 secret backstage lounge.
Be sure to come back at 3pm when the fourth puzzle will be posted.
The digits 1 to 9 must be entered into the 9×9 grid below following normal sudoku rules: each digit must appear exactly once in each row, column, and 3×3 block. Additionally, the grid also contains thermometers and inequalities.
In each grey thermometer, the number in the circular bulb is the smallest number, and the numbers increase as you move away from the bulb. The sums of the digits on a diagonal indicated by an arrow must satisfy the inequality shown by the arrow (if the sum of the digits on a diagonal is written at the start of the arrow, then the resulting inequality must be true).
In this smaller example puzzle, the digits 1 to 4 must appear in each row, column, and 2×2 block exactly once. Starting from the grey bulbs, the numbers increase along each thermometer; and the numbers in the cells highlighted in blue in the solution add to more than or equal to 7. The sums of the digits on the other
indicated diagonals satisfy the inequalities written by their arrows.
The digit in the cell shaded blue is a factor of the code.
More from Chalkdust
- Sophie Maclean and David Sheard speak to a very top(olog)ical mathematician!
- Adam Townsend sets the fifth and final puzzle. Can you solve it?
- Humbug sets the fourth puzzle. Can you solve it?
- TD Dang sets the second puzzle. Can you solve it?
- David Sheard explores the rich mathematics and history behind the Apollonian packing, and the cover of issue 11