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Le Monde puzzle [#990]

January 12, 2017

To celebrate the new year (assuming it is worth celebrating!), Le Monde mathematical puzzle came up with the following: Two sequences (x¹,x²,…) and (y¹,y²,…) are defined as follows: the current value of x is either the previous value or twice the previous value, while the current value of y is the sum of the values […]

Le Monde puzzle [#940]

November 11, 2016

A sudoku-like Le Monde mathematical puzzle: On a 3×3 grid, all integers from 1 to 9 are present. Considering all differences between adjacent entries, the value of the grid is the minimum difference. What is the maximum possible value? In a completely uninspired approach considering random permutations on {1,..,9}, the grid value can be computed […]

Le Monde puzzle [#977]

October 3, 2016

A mild arithmetic Le Monde mathematical puzzle: Find the optimal permutation of {1,2,..,15} towards minimising the maximum of sum of all three  consecutive numbers, including the sums of the 14th, 15th, and first numbers, as well as the 15th, 1st and 2nd numbers. If once again opted for a lazy solution, not even considering simulated […]

Le Monde puzzle [#967]

September 30, 2016

A Sudoku-like Le Monde mathematical puzzle for a come-back (now that it competes with The Riddler!): Does there exist a 3×3 grid with different and positive integer entries such that the sum of rows, columns, and both diagonals is a prime number? If there exist such grids, find the grid with the minimal sum? I […]

Le Monde puzzle [#965]

June 14, 2016

A game-related Le Monde mathematical puzzle: Starting with a pile of 10⁴ tokens, Bob plays the following game: at each round, he picks one of the existing piles with at least 3 tokens, takes away one of the tokens in this pile, and separates the remaining ones into two non-empty piles of arbitrary size. Bob […]