- Did you solve it? Are you smart enough to opt out of cookies?by Alex Bellos on May 17, 2021 at 4:00 pm
The solutions to today’s puzzlesEarlier today I set three puzzles from Terms & Conditions Apply, a free online game about website deviousness (that I made with Jonathan Plackett.) The puzzles in the game exaggerate the tricks websites use to extract our data. 1. Naughty negatives Continue reading…

- Can you solve it? Are you smart enough to opt out of cookies?by Alex Bellos on May 17, 2021 at 6:00 am
Puzzles about internet deviousnessUPDATE: Solutions can be read here.It’s a depressing fact of online life that websites are often shameless in using shady practices, like misdirection and obfuscation, to get us to sign up to, or to agree to, something we do not want.Today’s puzzles exaggerate the cunning tricks websites use to extract our personal data – but only just! Continue reading…

- To infinity and beyond: the spectacular sensory overload of Ryoji Ikeda’s artby Cleo Roberts-Komireddi on May 9, 2021 at 2:00 pm
Incandescent light, the thud of Tokyo nightclubs, particle physics … it all goes into Ryoji Ikeda’s extraordinary sensory symphonies. He talks about his upcoming show at 180 The StrandRyoji Ikeda has delivered some dazzling rushes on the senses over his 25-year career: a beach in Rio de Janeiro bathed in his unique palette of light; New York’s Times Square given over to his black and white flickering patterns. But for his next show, the Japanese artist and composer is taking things underground. Ikeda’s biggest exhibition in Europe to date concerns the exposed underbelly of 180 The Strand in London, which he has reimagined as staves, notes and bar lines – with himself as the conductor, “orchestrat[ing] everything into a symphony”.Beginning with a single light beam piercing the rafters, the exhibition carries the viewer through an incandescent corridor of white light and into a room filled with a ring of immense, super-directional speakers reverberating at concert pitch. To Ikeda, this is “opera” with light and sound. “There’s the intro, the welcome piece, then the crescendo [and] climax. It’s a long journey.” Continue reading…

- How good are we at predicting the pandemic? | David Spiegelhalter & Anthony Mastersby David Spiegelhalter and Anthony Masters on May 9, 2021 at 7:00 am
Models have been useful, especially as humans are far too optimistic and confidentEpidemiological models have been a source of continual controversy from the start of the pandemic, often blamed for fearmongering and inaccuracy. How well have they done?Perhaps the most famous piece of modelling came from Neil Ferguson’s team at Imperial College London in March 2020, credited with provoking the full national lockdown. Unfortunately, there are repeated claims they estimated 510,000 deaths in Great Britain over two years, but that was a projection under the implausible scenario that nothing was done about the virus. Their model was, if anything, rather optimistic. Even short of a full lockdown, they projected maximum deaths in Great Britain of fewer than 50,000 and the actual total has been far higher. Continue reading…

- Did you solve it? A tray of Portuguese delightsby Alex Bellos on May 3, 2021 at 4:00 pm
The solutions to today’s puzzlesEarlier today I set you four puzzles by Paulo Ferro, a Portuguese puzzle maker.1. Trapezium or trap-not-so-easy-um? Continue reading…

- Can you solve it? A tray of Portuguese delightsby Alex Bellos on May 2, 2021 at 11:00 pm
Custard tarts for the brainUPDATE: The solutions are now up here.Today, four tasty treats from Paulo Ferro, a puzzlesmith from Porto.1. Trapezium or trap-not-so-easy-um? Continue reading…

- Free will debate rages on, or is it all an illusion? | Lettersby Letters on May 2, 2021 at 3:29 pm
Readers reflect on the role of chance, randomness and responsibility in their own livesWhat high-quality letters (29 April) on free will. My A-level psychology students always found this fascinating and usually thought that free will was obvious until they had examined their own lives and realised that “soft determinism”, well-expounded by Robert Dimmick, was the likely answer. However, there is a big role for chance.For example, I probably wouldn’t have been born in 1949 if my father hadn’t dropped a large tin of paint and shattered his foot while painting the cruiser that he was on during the second world war. His ship sailed without him and was sunk by Japanese bombers with massive loss of life. My father didn’t choose to drop the paint pot, but thereafter there were broad deterministic tramlines to his and my life.Philip WoodKidlington, Oxfordshire Continue reading…

- Nicholas Britton obituaryby Suzanne Skevington on April 30, 2021 at 11:24 am
My husband, Nicholas Britton, who has died aged 67 of bone cancer, was a pioneering mathematical biologist whose research covered a huge range of subjects, from how malaria is transmitted to the growth of tree rings, and dialects in bird song.His teaching and work on modelling techniques made an important contribution to inspiring and training the generation of researchers who are currently applying these skills and knowhow to solving the problems of the Covid-19 pandemic. Continue reading…

- Did you solve it? Are you smarter than Britain’s teenage brainiacs?by Alex Bellos on April 19, 2021 at 4:00 pm
The solutions to today’s puzzlesEarlier today I set you the following two puzzles. The first is from the UK’s Mathematical Olympiad for Girls:Painting the housesYYWYWY WYY Continue reading…

- Can you solve it? Are you smarter than Britain’s teenage brainiacs?by Alex Bellos on April 19, 2021 at 6:10 am
A colourful puzzle from the UK girls’ maths olympiadUpdate: the solutions can now be read here.Today’s puzzle celebrates the UK’s outstanding performance at last week’s European Girls’ Mathematical Olympiad, which is the world’s most prestigious female-only maths competition for pre-university students.Yuhka Machino and Jenni Voon, both aged 17, placed 6th and 7th overall, each earning gold medals. Overall, the UK ranked fifth out of 55 countries, behind Russia, the USA, Peru and Romania. (The event was held online, allowing 17 non-European countries to participate as guests.) Continue reading…

- The obscure maths theorem that governs the reliability of Covid testingby Tom Chivers on April 18, 2021 at 6:00 am
There’s been much debate about lateral flow tests – their accuracy depends on context and the theories of a 18th-century clericCoronavirus – latest updatesSee all our coronavirus coverageMaths quiz. If you get a positive result on a Covid test that only gives a false positive one time in every 1,000, what’s the chance that you’ve actually got Covid? Surely it’s 99.9%, right?No! The correct answer is: you have no idea. You don’t have enough information to make the judgment.Without knowing the prior probability, you don’t know how likely it is that a result is false or true Continue reading…

- Did you solve it? Tasty buns for Easter eggheadsby Alex Bellos on April 5, 2021 at 4:00 pm
The solutions to today’s puzzlesEarlier today I set you two puzzles by the veteran US puzzle inventor Sam Loyd.1. The famous hot cross bun puzzle Continue reading…

- Did you solve it? The crazy maths of cryptoby Alex Bellos on March 22, 2021 at 5:00 pm
The solution to today’s puzzle about trust, secrets and the world’s weirdest proofEarlier today I set the following puzzle, based on the remarkable mathematical concept of a ‘zero-knowledge proof,’ which has applications in cyber security. (To find out why this concept is so revolutionary, and how it relates to the puzzle, you can read the original article here.)The stolen paper clip Continue reading…

- Can you solve it? The crazy maths of cryptoby Alex Bellos on March 22, 2021 at 7:10 am
A puzzle about trust, secrets, and the world’s weirdest proofUPDATE: The solution can be read hereToday’s puzzle is based on a ground-breaking mathematical concept which last week won one of its pioneers the Abel Prize, considered the Nobel Prize of maths.The concept is the zero-knowledge proof, and it has many applications in digital cryptography. Let me briefly explain.STEP 1 You and Annabel agree on a way to allocate a number from 1 to 100 to everyone in the office.STEP 2 You write down the number of the person you suspect on a piece of paper. Annabel does the same.STEP 3 You hand Dan the two pieces of paper, and you ask him to tell you if both pieces have the same number. Continue reading…

- Did you solve it? We are (puzzle) familyby Alex Bellos on March 8, 2021 at 5:00 pm
I got all my solutions with meEarlier today I set you the following two puzzles:1. The two sisters Continue reading…

- Can you solve it? We are (puzzle) familyby Alex Bellos on March 8, 2021 at 7:14 am
I got all my street smarts with meUPDATE: Read the solutions here.It’s March, so let’s begin with this riddle:1. The two sisters Continue reading…

- Did you solve it? The art of the puzzleby Alex Bellos on February 22, 2021 at 5:00 pm
The solutions to today’s artful problemsEarlier today I set you the following puzzles. The first is a starter problem and the other three were suggested by puzzle guru Rob Eastaway.The nine dotsa) Barely get their fingers underneathb) Crawl underc) Get under if they crouchd) Comfortably walk under Continue reading…

- Can you solve it? The art of the puzzleby Alex Bellos on February 22, 2021 at 7:38 am
Thinking in and out of the boxUPDATE: The solutions are now up hereWhat makes for a great puzzle? Here’s a golden oldie that certainly qualifies.The nine dotsAn ‘aha’ momentA surprising, counter-intuitive outcomeVisually appealingWhimsically writtenRequires little background expertiseConcisely statedPleasurably teasing: looks very simple but isn’tEasy entry pointa) Barely get their fingers underneath.b) Crawl under.c) Get under if they crouch.d) Comfortably walk under. Continue reading…

- Did you solve it? Think of a numberby Alex Bellos on February 8, 2021 at 5:00 pm
The solution to today’s Q&A puzzleEarlier today I asked you the following puzzle.Ask Johnny Continue reading…

- Can you solve it? Think of a numberby Alex Bellos on February 8, 2021 at 7:12 am
A new twist on the all time classic maths trick UPDATE: the solution can now be read here.“Think of a number” tricks are such a puzzle staple that the BBC even named a kids show after them. (To readers under the age of 40, Think of a Number was hosted by Zoe Ball’s dad Johnny, and to many Britons, this one included, it was an indelible cultural highlight of growing up in the late 1970s/early 1980s.)The following puzzle is a brilliant version of a ‘think of a number’ type problem, which I had not seen until recently. The solution is wonderfully ingenious. If you don’t crack it now, or at all (as it consumes your day, sorry), you will be rewarded when I reveal the answer at 5pm.1 and 500? Yes.1 and 250? No.251 and 375? Yes.251 and 313? No.314 and 345? No.346 and 361? Yes.346 and 354? No355 and 358? Yes355 and 356? NoIs it 358? Yes! (a No here gets you the answer too.) Continue reading…