# Posts Tagged ‘ Le Monde ’

## Le Monde puzzle [42]

October 24, 2010
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An interesting suduko-like puzzle for this week puzzle in Le Monde thi A 10×10 grid is filled by a random permutation of {0,…,99}. The 4 largest figures in each row are coloured in yellow and the 4 largest values in each column are coloured in red. What is the range of the number of yellow-and-red

## Le Monde puzzle [41]

October 17, 2010
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The current puzzle in Le Monde this week is again about prime numbers: The control key on a credit card is an integer η(a) associated with the card number a such that, if the card number is c=ab, its key η(c) satisfies η(c)=η(a)+η(b)-1. There is only one number with a key equal to 1 and

## Le Monde puzzle [40]

October 10, 2010
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The puzzle in Le Monde this week is called the “square five” (sic!): Two players each have twenty-five cards with five times each of the digits 1,2,3,4,5. They alternate putting one card on top of the pile, except that they can instead take an arbitrary number of consecutive cards from the top of the pile

## Le Monde puzzle [34]

October 3, 2010
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Since the puzzle in this week (-end) edition of Le Monde is not (easily) solvable via an R program, I chose to go back to an older puzzle that my students can solve. Eleven token are distributed around a 200 meter perimeter-long ring. They all start moving at the same speed, 18km/h, in

## Le Monde puzzle [38]

September 29, 2010
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Since I have resumed my R class, I will restart my resolution of Le Monde mathematical puzzles…as they make good exercises for the class. The puzzle this week is not that exciting: Find the four non-zero different digits a,b,c,d such that abcd is equal to the sum of all two digit numbers made by picking

## Candy branching process

May 5, 2010
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$Candy branching process$

The mathematical puzzle in the latest weekend edition of Le Monde is as follows: Two kids are given three boxes of chocolates with a total of 32 pieces. Rather than sharing evenly, they play the following game: Each in turn, they pick one of the three boxes, empty its contents in a jar and pick

## Le Monde rank test (corr’d)

April 6, 2010
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$Le Monde rank test (corr’d)$

Since my first representation of the rank statistic as paired was incorrect, here is the histogram produced by the simulation perm=sample(1:20) saple=sum(abs(sort(perm)-sort(perm))) when . It is obviously much closer to zero than previously. An interesting change is that the regression of the log-mean on produces > lm(log(memean)~log(enn)) Call: lm(formula = log(memean) ~ log(enn)) Coefficients: (Intercept)

## Le Monde rank test

April 4, 2010
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$Le Monde rank test$

In the puzzle found in Le Monde of this weekend, the mathematical object behind the silly story is defined as a pseudo-Spearman rank correlation test statistic, where the difference between the ranks of the paired random variables and is in absolute value instead of being squared as in the Spearman rank test statistic. I don’t

## Solving the rectangle puzzle

March 15, 2010
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$Solving the rectangle puzzle$

Given the wrong solution provided in Le Monde and comments from readers, I went to look a bit further on the Web for generic solutions to the rectangle problem. The most satisfactory version I have found so far is Mendelsohn’s in Mathematics Magazine, which gives as the maximal number for a grid. His theorem is

## Wrong puzzle of the week [w10]?!

March 12, 2010
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In the weekend supplement to Le Monde, the solution of the rectangle puzzle is given as 32 black squares. I am thus… puzzled!, since my R program there provides a 34 square solution. Am I missing a hidden rectangle in the above?! Given that the solution in Le Monde is not based on a precise