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Le Monde puzzle [#882]

October 14, 2014

A terrific Le Monde mathematical puzzle: All integers between 1 and n² are written in an (n,n)  matrix under the constraint that two consecutive integers are adjacent (i.e. 15 and 13 are two of the four neighbours of 14). What is the maximal value for the sum of the diagonal of this matrix? Indeed, when considering […]

Le Monde puzzle [#879]

September 21, 2014

Here is the last week puzzle posted in Le Monde: Given an alphabet with 26 symbols, is it possible to create 27 different three-symbol words such that all symbols within a word are different all triplets of symbols are different there is no pair of words with a single common symbol Since there are 28x27x26/3×2=2925 […]

Le Monde puzzle [#875]

July 12, 2014

I learned something in R today thanks to Le Monde mathematical puzzle: A two-player game consists in A picking a number n between 1 and 10 and B and A successively choosing and applying one of three transforms to the current value of n n=n+1, n=3n, n=4n, starting with B, until n is larger than […]

Le Monde puzzle [#872]

June 28, 2014

An “mildly interesting” Le Monde mathematical puzzle that eventually had me running R code on a cluster: Within the set {1,…,56}, take 12 values at random, x1,…,x12. Is it always possible to pick two pairs from those 12 balls such that their sums are equal? Indeed, while exhaustive search cannot reach the size of the […]

Le Monde puzzle [#869]

June 8, 2014

An uninteresting Le Monde mathematical puzzle: Solve the system of equations a+b+c=16, b+c+d=12, d+c+e=16, e+c+f=18, g+c+a=15 for 7 different integers 1≤a,…,g≤9. Indeed, the final four equations determine d=a-4, e=b+4, f=a-2, g=b-1 as functions of a and b. While forcing 5≤a, 2≤b≤5, and  7≤a+b≤15. Hence, 5 possible values for a and 4 for b. Which makes […]

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