Archive for competition

Le Monde puzzle [#1003]

Posted in Kids, R with tags , , , on April 18, 2017 by xi'an

A purely arithmetic Le Monde mathematical puzzle:

Find the four integers w, x, y, z such that the four smallest pairwise sums among the six pairwise sums are 59, 65, 66, and 69. Similarly, find the four smallest of the five integers v, x, y, z such that the five smallest pairwise sums among the ten pairwise sums are 56, 64 , 66, 69 and 70.

The first question is rather straightforward since there are only two possible orderings when x≤y≤z≤w :

x+y≤x+z≤x+w≤y+z≤y+w≤z+w and x+y≤x+z≤y+z≤x+w≤y+w≤z+w

which means

x+y=59, x+z=65, x+w=66, y+z=69, and x+y=59, x+z=65, y+z=66, x+w=69

but since the first system does not allow for an integer solution, the only possibility is the second system, with solution (x,y,z,w)=(29,30,36,40). And the second question is of the same complexity, with, when x≤y≤z≤w≤v :

x+y=56, x+z=64, y+z=66, x+w=69, x+v=70 or x+y=56, x+z=64, x+w=66, x+v=69, y+z=70

with solutions (x,y,z,w,v)=(27,29,37,42,43) and (x,y,z,w,v)=(25,31,39,41,44).

Le Monde puzzle [#1000…1025]

Posted in Kids, R with tags , , , , , , on March 28, 2017 by xi'an

Le Monde mathematical puzzle launched a competition to celebrate its 1000th puzzle! A fairly long-term competition as it runs over the 25 coming puzzles (and hence weeks). Starting with puzzle #1001. Here is the 1000th puzzle, not part of the competition:

Alice & Bob spend five (identical) vouchers in five different shops, each time buying the maximum number of items to get close to the voucher value. In these five shops, they buy sofas at 421 euros each, beds at 347 euros each, kitchen appliances at 289 euros each, tables at 251 euros each and bikes at 211 euros each, respectively. Once the buying frenzy is over, they realise that within a single shop, they would have spent exactly four vouchers for the same products. What is the value of a voucher?

Paris-Dauphine photograph competition [jatp]

Posted in pictures, University life with tags , , , , , , on March 22, 2017 by xi'an

my ISBA tee-shirt designs

Posted in Books, Kids, pictures, Statistics, University life with tags , , , , , , , on October 15, 2014 by xi'an

Here are my tee-shirt design proposals for the official ISBA tee-shirt competition! (I used the facilities of as I could not easily find a free software around. Except for the last one where I recycled my vistaprint mug design…)


While I do not have any expectation of seeing one of these the winner (!), what is your favourite one?!

thumbleweed news [short story poll]

Posted in Books, Kids, pictures with tags , , , , , , , , , on November 10, 2013 by xi'an

Although I alas received only three submissions (#a, #b, and #c), following my call for thumb-related short stories, I may as well go and have a poll (for two weeks) as to which one was most appreciated by ‘Og’s readers… (I just noticed you cannot put links within the poll answers, most annoyingly!)

thumbleweed news [short story #c]

Posted in Books, Kids with tags , , , , , , , on October 1, 2013 by xi'an

Following the previous thumbleweed news, here is a third short story, called #c for the time being. There are a few days left for those who want to contribute to this series!

X woke up with a terrible hang over. Thinking of last night performance, he was proud himself. He is an equilibrist and has been lucky enough to perform at the biggest collaborative circus show in France. He has never seen so many talented and attractive people performing together and this is what he has been dreaming about. 

X was about to get a cup of water and noticed that his right thumb was gone and, wrapped. ‘This must be a horrible dream.’ he thought. Unfortunately, it wasn’t. He tried to remember what happened but all he could remember were some brief moments. After the show, there was a big party to celebrate the last performance. He had a great time till Tim started a fight again. Tim (a lion tamer) was always jealous of X’s talent. Tim got aggressive and threatened X with his lions. ‘His lion took my thumb?’ X got so furious at Tim then, he remembered the moment with Bella. Bella has been working on a hand disappearing magic. Yes, he was drunken enough to volunteer himself for her working magic. She brought an axe to pretend cut his hand. ‘So… my thumb got cut for real?’ He should’ve took Jimmy’s advice, ‘Never volunteer yourself to working magic.’ Last night Jimmy was too busy impressing Liz who was very popular and snobby. X was keen on Liz’s friend, Cloe, secretively. One moment, all of them were sitting at the same table and Liz whispered X that Cloe fascinated a snake show very much. Luckily (?) a group of Indian magicians was sitting at the next table. Yes, he remembered reaching out himself to those snakes for one simple purpose. 

‘My thumb must be beaten and poisoned?’ 

He got confused with these slices of memory and none of them gave him clear reason why he lost his thumb. He got out of his room and found Jimmy and Kev. 

Both looked at X worried. “How are you feeling? We were so afraid that we might lose you. You’ve been in a bed for four days.” Jimmy said. The most surprising question was asked by Kev, “So, what happened, X? How did you end up in the 5th district?” When a milkman found X next morning in the 5th district, his thumb was brutally smashed and even his bone. When he was brought to a surgeon, there was no other option except cutting his thumb. They talked to everyone and tried to find any clue. No one seems to know exactly what happened that night rather most of them couldn’t remember. 

After that, X, Jimmy and Kev traveled around countryside and performed together. After a year and half, that night seemed to be almost forgotten till one morning X read a small article. It was about the new invention of a punch press machine and there was a photo of an inventor, Cloe, smiling beautifully. One of feature caught his eyes, ‘Warning : The maximum pressure is enough to crush human hand.‘

thumbleweed news [short story #b]

Posted in Books, Kids with tags , , , , , , , on August 3, 2013 by xi'an

Following the previous thumbleweed news, here is a second short story, called… #b for the time being, that sounds more on a realistic plane than #a:

The din was deafening, literally deafening. One hundred and ten kids, drunk on sun, sea and the urge to enjoy a last and final day of freedom together before returning to their respective families after this too short summer camp. As it happened, the dining hall was a large barn with high ceiling, white walls and thin roofs, storing heat and noise like no other place in those hot summer days. The shouts and conversations were rising like so many waves, only to break against the next shouts and conversations. But this did not prevent the kids from eating whatever fell in their plate. Or in their neighbours’! They had cleaned dry the bones of the mackerels I had spent the whole afternoon gutting and cleaning after a fisherman showed up with a basket of leftovers from the morning market. And there was not a single slice remaining from the potatoes I had peeled and cut over the morning. I had already refilled the bread baskets once  and now they wanted more, to get with the salad bowls I had just dropped on the tables…

Getting back to the camp kitchen was a relief from both the heat and the noise. Its heavy stone walls were protection enough and the oven were cold as we had cooked the mackerels on grills outside. More cleaning to do later, though. The poor lighting due to narrow and dusty windows helped in this feeling of relative coolness. I dropped my baskets on a table and looked around: fortunately there was enough bread left in the scullery and I took several loaves next to the manual bread slicer. I had grown expert over the past weeks at working the slicer with high efficiency, pushing the break with one hand while quickly pumping the handle and the blade with the other. This was my only recipe at the moment to prevent a riot in the dinner hall! Anyway, I did not want to see any one and especially no kid near this machine. 

I had already filled two baskets and I looked at the third one as the loaf was steadily disappearing under the blade. I was actually much closed to its end than I thought and pushed my thumb through the gap with the rest of the loaf. It all happened so quickly that in the heat of the moment I first fail to notice anything was wrong. Only when the bread slices came out crimson did I realise I had cut myself. I nonetheless had to look at my hand to see the bleeding stump and understand my thumb was gone. I could see it lying there in the crumb collector under the machine, not much distinguishable from a bread piece in the uncertain light. The cut had been sharp and instantaneous, thanks to the weight of the blade, so sharp that I was not in pain but just stunned and shocked, unable to move or speak or act in any coherent way, staring at this impossible transformation of my hand. However, my body defences quickly took over and I soon fainted on the kitchen cool floor. Before the pain really hit.

When I woke up, staring at the wooden ceiling and its cobwebs, I tried to resist the unavoidable reality, to block sound and feeling and mind away in a world where nothing had happened, in another plane where the floor and the thumb were far below me, in another structure with no pain but only the sounds of the waves breaking on the rocks outside the house and of the gulls calling one another in the evening light. I could not stay there long enough and came back to my floor to realise the main cook had wrapped the stump in a clean white cloth, then put ice cubes around. I could not see the thumb any longer. The kitchen was still quiet and cool, with the cook holding my head against her knees with her other hand. Someone had clearly gone to call emergency for an ambulance came to take me to the hospital a few minutes later. I left the camp unobserved by the kids: the din from the hall had not abated a bit.

To this day, a basket of bread slices never fail to wake in me the memory of this hot and intense noise that reverberated from the hall roofs. Never the memory of a bread slicer, surprisingly…