Perfect Numbers and Mersenne Primes



Funbers Christmas Special

A very fun Christmas treat for you all as I team up with my good friend Bobby Seagull for the Funbers Xmas Special – expect fun facts, lots of numbers, and more birds than anyone thought possible… Happy Holidays!!

12 Days of Christmas Puzzles

Looking for some festive fun over the holiday season? Why not try your hand at my 12 Christmas puzzles…

Answers to all puzzles at the bottom of the page. 


Puzzle 1: If I set a puzzle every day of the advent period (1-25 December) and spend 1 minute on the first puzzle, 2 minutes on the second, 3 minutes on the third, and so on, with the final one being 25 minutes on the 25th puzzle, what is the total amount of time I will spend writing puzzles?



Puzzle 2: December 6th marked my birthday and to celebrate I travelled to Kiev with 4 friends. If I order a drink on the flight out and then each of my friends orders twice as many as the person before, how many drinks do we order in total?



Puzzle 3: This morning I built a snowman using three spheres of radius 0.5m, 0.4m and 0.2m. However, the sun has since come out and the snowman is starting to melt at a rate of 0.01 m3 per minute. How long will it take for him to disappear completely?



Puzzle 4: Suppose a newly-born pair of elves, one male, one female, are living together at the North pole. Elves are able to mate at the age of one month so that at the end of its second month a female elf can produce another pair of offspring. Suppose that the elves never die, and that the female always produces one new pair (one male, one female) every month from the start of the third month on. After one year, how many pairs of elves will there be?



Puzzle 5: On Christmas day I have 11 people coming to dinner and so I’m working on the seating plan ahead of time. For a round table with exactly 12 chairs, how many different seating plans are possible?



Puzzle 6: My front yard is covered in snow and I need to clear a path connecting my front door to the pavement and then back to the garage. If each square in the diagram is 1m x 1m what is the shortest possible path?



Puzzle 7: The first night of Chanukah is December 22nd when the first candle is lit. If it burns at a rate of 0.05cm per hour, how tall does the candle need to be to last the required 8 days?



Puzzle 8: If you have a square chimney which is 0.7m across, assuming Santa has a round belly what is the maximum waist size that can fit down the chimney?



Puzzle 9: On Christmas Eve Santa needs to visit each country around the world in 24 hours. Assuming time stands still whilst he is travelling, how long can he spend in each country?



Puzzle 10: I got carried away with buying presents this year and now have more than can fit into my stocking. If the stocking has a maximum capacity of 150, and my presents have the following sizes: 16, 27, 37, 65, 52, 42, 95, 59; what is the closest I can get to filling the stocking completely?

(NB: I am not looking for the highest number of presents that will fit, but the largest total that is less than or equal to 150).



Puzzle 11: Santa has 8 reindeer, and each one can pull a weight of 80kg. If Santa weights 90kg, his sleigh 180kg, and each present weighs at least 3kg, what is the maximum number of presents that can be carried in a single trip?



Puzzle 12: To mark the end of the 12 days of Christmas each student at the University of Oxford has kindly decided to donate some money to a charity of their choice. If the first person donates £12 and everyone after donates exactly half the amount of the person before them (rounding down to the nearest penny), how much will be donated in total?





Puzzle 1: 1 + 2 + 3 + … + 25 = 325. There is a faster way to do this which was first discovered by the mathematician Gauss when he was still at school. If you pair each of the numbers in your sum, eg. 0 + 25, 1 + 24, 2 + 23, etc. up to 12 + 13, then you have 13 pairs which each total 25 and so the overall total is 25*13 = 325. The same method works when adding up the first n numbers, with the total always being n(n+1)/2.



Puzzle 2: 1+2+4+8+16 = 31.



Puzzle 3: Volume of a sphere = (4/3)*pi*radius3 and so the total volume of snow = 0.52 + 0.27 + 0.03 = 0.82 m3. Melting at a rate of 0.01 m3 per minute means the snowman will be gone after only 82 minutes!



Puzzle 4: This problem is actually a very famous sequence in disguise…

The first new pair is born at the start of the third month giving 2 pairs after three months. The question tells us that we have to wait one whole month before the new offspring can mate and so only the original pair can give birth during the fourth month which leaves a total of 3 pairs after four months. For the fifth month, both the original pair, and the first-born pair can now produce offspring and so we get two more pairs giving a total of 5 after five months. In month six, the second-born pair can now also produce offspring and so in total we have three offspring-producing pairs, giving 8 pairs after 6 months.

At this point, you may have spotted that the numbers follow the Fibonacci sequence, which is created by adding the previous two numbers together to get the next one along. The first twelve numbers in the sequence are below, which gives an answer of 144 – no wonder Santa is able to make so many toys!




Puzzle 5: I have 12 choices of where to place the first person, 11 for the second, 10 for the third and so on, which gives 12*11*10*9*8*7*6*5*4*3*2*1 = 12! (read as 12 factorial) in total. BUT for any given seating plan we can rotate around the table one place to get the same order, which means we have in fact over counted by a factor of 12. Therefore, the total number is 11! = 39,916,800.



Puzzle 6: Reflect the yard in the pavement and draw a straight line connecting the front door to the edge of the garage closest to the front door (blue). Then add the same line from the ‘reflected’ front door at the top back down to the garage at the bottom (orange). The final shortest path is found by combining both paths for a valid one in the original diagram.

Screenshot 2020-01-14 at 13.04.44

The length is found using Pythagoras’ Theorem. From the door to the pavement we have length

(12 + 22)1/2 = (5)1/2

and from the pavement to the garage the length is

((1.5)2 + 32)1/2 = (11.25)1/2

giving a total length of 2.23 + 3.35 = 5.58m.



Puzzle 7: 8 days = 8*24 hours = 192 hours. 192*0.05 = 9.6cm.



Puzzle 8: Chimney diameter = 0.7m so the maximum circumference (or waist size) that will fit is 0.7*pi = 2.2m or 88 inches!



Puzzle 9: Using the UN list of 193 countries, Santa has 24 * 60 = 1440 minutes total, which means spending only 7.5 minutes in each country!



Puzzle 10: 150 exactly with 16 + 27 + 42 + 65 = 150.



Puzzle 11: We have 8 reindeer each with a capacity of 80kg giving a total of 640kg that can be carried. Subtracting the 90kg for Santa and 180kg for the sleigh leaves 370kg available. Dividing this by 3 gives 123.33 so a maximum of 123 presents can be carried at once.



Puzzle 12: 12 + 6 + 3 + 1.5 + 0.75 + 0.37 + 0.18 + 0.09 + 0.04 + 0.02 + 0.01 + 0 + 0 + 0 + …

The donations stop after the 11th person giving a total of £23.87. Even if we had allowed donations of part of a penny the total would never quite reach £24.00. This is an example of an infinite sum (or Geometric Series) where the total is always two times the first number.

How does Sea Ice affect Climate Change?

There is no doubt that sea ice in the polar regions is melting, but what is the exact role that this plays in the global climate system? To understand climate change we need to understand mixing in the ocean, which is exactly what Andrew Wells at the University of Oxford comes is trying to do by studying a model for sea ice growth in the Arctic.



Tom Rocks Maths S2 E12

Season 2 comes to a close with stories from my (rather eventful) trip to China, a new video series with BBC Maths Guru Bobby Seagull, and the number of calories needed by a Charizard per day to survive. That’s all on top of the usual puzzle and fun facts about the numbers 0 and 1. Plus, music from the Red Hot Chili Peppers, System of a Down, and Limp Bizkit. This is maths, but not as you know it…


  • 00:00 Opening
  • 00:13 Bowling for Soup – Normal Chicks
  • 03:25 Limp Bizkit – My Generation
  • 07:05 Red Hot Chili Peppers – The Adventures of Rain Dance Maggie
  • 11:44 News
  • 18:00 Enter Shikari – Arguing with Thermometers
  • 21:22 Puzzle
  • 24:09 System of a Down – Shimmy
  • 25:59 Atreyu – You Gave Love a Bad Name
  • 29:22 Pokemaths: How many calories does a Charizard need per day?
  • 38:13 Midtown – Get it Together
  • 41:30 Billy Talent – Nothing to Lose
  • 45:02 Funbers 0 and 1
  • 51:36 The Story So Far – Right Here
  • 54:02 Puzzle Solution and Close

Tom Rocks Maths S02 E11

A special edition of Tom Rocks Maths on Oxide Radio with music inspired by Tom’s recent visit to Slam Dunk Festival. We’ve also got Pokemon and drinking games, a mind-bending Einstein Puzzle, and news of Tom’s antics running around the streets of Oxford in his underwear… This is maths, but not as you know it.

Maths with a Striptease (Die Rheinpfalz)

Tom “rocks” maths on the internet – lecturer from Oxford arouses enthusiasm with crazy ideas… 

The graduate mathematician Tom Crawford not only has rock music as a hobby, but he also looks like a rock star with his tattoos and piercings. However, some of his tattoos are related to mathematics. For example, the first 100 decimal places of Euler’s number wind around his arm and the number pi has been encrypted as an infinite series. On his Youtube channel “Tom Rocks Maths” he presents science in a fun way – the clothes sometimes fly during a striptease: “I want to show that maths is not always only downright serious, but fun.”

The math lecturer from Oxford came as part of the Heidelberg Laureate Forum (HLF) in the Electoral Palatinate. Since there is no Nobel Prize in mathematics, the winners (Latin: laureates) of comparable awards are invited to the HLF. The best math and computer scientists in the world meet here for a week with junior scientists and journalists. Crawford was on the ground as a publicist and presenter, and took the opportunity to speak to some of the awardees. For example, Martin Hairer, who received the Fields Medal for his seminal studies, had an appointment for an interview. In the end, they played Tetris for an hour and talked about “cool math”: “Such a relaxed and profound conversation is only possible at the Heidelberg Laureate Forum,” the Brit enthuses about the inspiring atmosphere at the HLF.


Tom Crawford was already “packed” in the elementary school of mathematics: “When we were learning multiplication, I did not want to stop working on difficult tasks until late in the evening – it did not feel like work at all.” Even later in high school, he always did math tasks first and gladly. “I was a good student in my eleven subjects, but math was the most fun.” The satisfying thing is, “in maths a result is right or wrong, there is no need to discuss it.”

After studying in Oxford, he went to Cambridge to write his PhD in fascinating  fluid dynamics. “We wanted to model how fluids move and interact with the world. I was excited about the prospect of being able to analyse experiments as a mathematician.” From this, models of reality were developed: what path does a river take when it flows into the sea? The findings help to understand the pollution of the oceans and possibly stop it. During his PhD he worked for the BBC in the science programme “The Naked Scientists”: this meant that the scientists liberated their theories from the complicated “clothes” and reduced them to a comprehensible basis. In this way, a layman will discover “naked” facts – in the sense of comprehensible ones. The radio broadcasts were a great success.”But you also have to visualize maths,” so he started to make his own videos and took the concept of the “naked mathematician” literally. In some lectures, he reveals the equations “layer by layer” and in each stage falls a garment – until Tom remains only in his boxer shorts. And then his tattoos are also visible, on whose mathematical background he will give a lecture in Oxford soon – with many guests guaranteed!

With unusual ideas, the only 29-year-old mathematician arouses the desire and curiosity for his subject. His original internet activities have now been honoured with an innovation prize. Even when attending school in Schwetzingen Tom Crawford had unusual questions: “In the stomach of a blue whale 30 kilos of plastic have been found: How much would that be if a person swallows just as much in relation to their own body weight?” The students calculated that in the human stomach, six (empty) plastic shopping bags would be located. Or, “How many table tennis balls are needed to lift the sunken Titanic off the ground?” And which example impressed him most in mathematics? “It is terrific how Maxwell’s equations, which deal first with electricity and magnetism, follow the wave property of light with the help of mathematics alone. Math is just fantastic! ”

Birgit Schillinger

The original article published in the Die Rheinpfalz newspaper (in German) is available here.

Tom Rocks Maths S02 E10


Image credit: Lou Stejskal

Struggling to engage your students with maths? Think outside the box…

New guidance, released by Pearson, says: If we want to tackle maths anxiety in Britain, we have to change the negative perceptions and experiences that so many learners have when it comes to maths. In this blog, Dr Tom Crawford, maths tutor at the University of Oxford, shares his take on the out-of-the-box approaches to help engage young people with the subject, spark curiosity and inspire life-long interest in maths.

Maths is boring, serious and irrelevant to everyday life – at least according to the results of my survey amongst friends, students and colleagues working in education. This isn’t necessarily something new, but it does highlight one of the current issues facing maths education: how do we improve its image amongst society in general?

With ‘Tom Rocks Maths’ my approach is simple: improve the image of maths by combatting each of the three issues identified above, and do it as creatively as possible…

Tackling “Maths is boring”

The misconception that maths is a boring subject often develops from maths lessons at school.  Due to the extensive curriculum, teachers do not have the time to explore topics in detail, and in many cases, resort to providing a list of equations or formulae that need to be memorised for an exam.

My attempted solution is to do the hard work for them by creating curiosity-driven videos that explain mathematical concepts in exciting and original ways. Take the example of Archimedes Principle – a concept that explains why some objects are able to float whilst others sink – a key part of the secondary school curriculum. It’s perhaps not the most engaging topic for teenagers with no interest in weight regulations for maritime vehicles. But, if instead the topic were presented as part of a video answering the question ‘how many ping-pong balls would it take to raise the Titanic from the ocean floor?’ then maybe we can grab their attention.

Generating curiosity-driven questions such as these is not always easy, but the core concept is to present the topic as part of the answer to an interesting question that your audience simply has to know the answer to.

When teaching my second-year undergraduate students about Stokes’ Law for the terminal velocity of an object falling through a fluid, we discuss the question ‘how long would it take for Usain Bolt to sink to the bottom of the ocean?’ – something I think almost everyone wants to know the answer to! (Don’t worry you can watch the video to find out).

Tackling “Maths is irrelevant to everyday life”

Of all of the issues facing maths in society at the moment, this is perhaps the one that annoys me the most. The majority of people that I speak to who don’t like maths will tell me that it’s the ‘language of the universe’ and can be used to describe pretty much anything, but yet they almost always go on to say how they stopped trying to engage with it because it simply doesn’t apply to them. This is what we mathematicians call a contradiction.

To try to tackle this issue, I go out of my way to present as large a range of topics as possible from a mathematical viewpoint. This has seen me discuss the maths of dinosaurs, the maths of Pokémon and the maths of sport to name but a few. Throughout 2018, my weekly ‘Funbers’ series with BBC radio examined the ‘fun facts about numbers that you didn’t realise you’ve secretly always wanted to know’, where each week a new number would be discussed alongside an assortment of relevant facts from history, religion and popular culture. When working with the BBC, I was very insistent that the programmes were introduced as a ‘maths series’ to help listeners to make the connection between maths and everyday life.

Tackling “Maths is too serious”

At first this surprised me. I’d never personally thought of my subject as ‘serious’ and speaking to my friends and colleagues, they seemed equally perplexed. But then it hit me. Looking at maths and mathematicians from the outside, where you cannot understand the intricate details and beautiful patterns, calling the subject ‘serious’ is a very valid response. There are endless rules and regulations that must be followed for the work to make sense, and most people working in the field can come across as antisocial or introverted to an outsider, which is where I come in.

To try to show that maths isn’t as serious as many people believe, and just to have some plain old fun, I created my persona as the ‘Naked Mathematician’. This began with the ‘Equations Stripped’ video series on YouTube, where I strip-back some of the most important equations in maths layer by layer, whilst also removing an item of my clothing at each step until I remain in just my underwear. As well as providing an element of humour to the videos (as no mention is made of the increasing lack of clothing), the idea is that by doing maths in my underwear it shows that it does not have to be taken as seriously as many people believe.

I have also seen an added benefit of this approach in attracting a new audience that otherwise may not have had any interest in learning maths – from my perspective I really don’t care why people are engaging with the subject, so long as they have a good experience which they will now associate with mathematics.

Whilst I am aware that my approach to tackling the issues faced by mathematics in society may not be to everyone’s tastes, our current methods of trying to engage people with maths are not working, so isn’t it about time we tried thinking outside of the box?

The original article published by Pearson is available here.

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