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IB Maths and GCSE Maths Resources from British International School Phuket. Theory of Knowledge (ToK). Maths explorations and investigations.  Real life maths. Maths careers. Maths videos. Maths puzzles and Maths lesson resources.

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British International School Phuket

Welcome to the British International School Phuket’s maths website. My name is Andrew Chambers and I am currently working at BISP.  I am running my site as the school’s maths resources website for both our students and students around the world.

We are a British international school located on the tropical island of Phuket in Southern Thailand. We offer a number of scholarships each year, catering for a number of national and international standard sports stars as well as for academic excellence. You can find out more about our school here.

There are a huge amount of resources to explore – especially for students doing their IAs and for students looking for revision videos.  You may also like to try our school code breaking site – where you can compete with over 10,000 students from around the world who have made it onto our school leaderboard.


pyramidThe Mathematics of Cons – Pyramid Selling

Pyramid schemes are a very old con – but whilst illegal, still exist in various forms. Understanding the maths behind them therefore is a good way to avoid losing your savings!

The most basic version of the fraud starts with an individual making the following proposition, “pay me $1000 to join the club, all you then need to do is recruit 6 more people to the club (paying $1000 each) and you will have made a $5000 profit.”

There are lots of variations – and now that most people are aware of pyramid selling, now normally revolve around multi-level-marketing (MLM).  These are often still pyramid schemes, but encourage participants to believe it is a genuine business by actually having a sales product which members have to sell.  However the main focus of the business is still the same – taking money off people who then make their money back after having signed up a set number of new recruits.

The following graphic from Consumer Fraud Reporting is a clear mathematical demonstration why these frauds only end up enriching those at the top of the pyramid:

pyramid 2You can see that if the requirement was to recruit 8 new members, that by the 9th level you would need to have 1 billion people already signed up.  Even with the need to recruit just 4 new members you still have rapid exponential growth which very quickly means you will run out of new potential members.  For pyramid schemes it is only those in the first 3-4 levels (the white cells) that stand any real chance of making money  – and these levels are usually filled by those in on the scam.

Ponzi schemes (like that run by Bernie Madoff) use a similar method.  A conman takes money from investors promising (say) 10% annual returns.  Lots of investors sign up.  The conman then is able to use the lump sum investments to pay the 10% annual returns.  This scam can last for years, with people thinking that they are getting a good rate of return, only to find out eventually that actually their lump sum investment has gone.

This is a good topic to look at with graphs (plotting exponential growth), interest rates, or exponential sequences – and shows why understanding maths is an important financial skill.

If you like this topic you might also like:

Benford’s Law – Using Maths to Catch Fraudsters – the surprising mathematical law that helps catch criminals.

Amanda Knox and Bad Maths in Courts – when misunderstanding mathematics can have huge consequences .

Which Times Tables do Students Find Difficult?

There’s an excellent article on today’s Guardian Datablog looking at a computer based study (with 232 primary school students) on which times tables students find easiest and difficult.  Edited highlights (Guardian quotes in italics):

Which multiplication did students get wrong most often?

times tables1

The hardest multiplication was six times eight, which students got wrong 63% of the time (about two times out of three). This was closely followed by 8×6, then 11×12, 12×8 and 8×12.

The graphic shows the questions that were answered correctly the greatest percentage of times as dark blue (eg 1×12 was answered 95% correctly).  The colours then change through lighter shades of blue, then from lighter reds to darker reds.  It’s interesting to see that the difficult multiplications cluster in the middle – perhaps due to how students anchor from either 5 or 10 – so numbers away from both these anchors are more difficult.

Which times table multiplication did students take the longest time to answer?

times tables2

Maybe unsurprisingly, 1×1 got answered the quickest (but perhaps illustrating the hazards of speed, pupils got it wrong about 10% of the time), at 2.4 seconds on average – while it was 12×9 which made them think for longest, at an average of 7.9 seconds apiece.

It’s quite interesting to see that this data is somewhat different to the previous graph.  You might have expected the most difficult multiplications to also take the longest time – however it looks as though some questions, whilst not intuitive can be worked out through mental methods (eg doing 12×9 by doing 12×10 then subtracting 12.)

How did boys and girls differ?

On average, boys got 32% of answers wrong, and took 4.2 seconds to answer each question.  Girls, by contrast, got substantially fewer wrong, at 22%, but took 4.6 seconds on average to answer.

Another interesting statistic – boys were more reckless and less considered with their answers!  The element of competition (ie. having to answer against a clock) may well have encouraged this attitude.  It would be interesting to see the gender breakdown to see whether boys and girls have any differences in which multiplication they find difficult.

Which times table was the hardest?

times tables 3

As you might expect, overall the 12 times table was found most difficult – closely followed by 8.   The numbers furthest away from 5 and 10 (7,8,12) are also the most difficult.  Is this down to how students are taught to calculate their tables – or because of the sequence patterns are less memorable?

This would be a really excellent investigation topic for IGCSE, IB Studies or IB SL.  It is something that would be relatively easy to collect data on in a school setting and then can provide a wealth of data to analyse.  The full data spreadsheet is also available to download on the Guardian page.

If you enjoyed this post you may also like:

Finger Ratio Predicts Maths Ability?– a maths investigation about finger ratio and mathematical skill.

Premier League Finances – Debt and Wages – an investigation into the finances of Premier League clubs.

Wau: The Most Amazing Number in the World?

This is a fantastic video from Vi Hart of Khan Academy. Watch it first and marvel at the properties of this amazing number:

Once you have watched it, watch it again – this time thinking about what number Wau might be – and why you have never heard of Wau before.

This is a great video to show to students – especially IB students, who once they have figured it out can go through the video and see why the infinite sequences, the imaginary numbers, the repeated powers etc all work. There’s one mistake in the video – which is flagged by an annotation. Turn of the annotation and see if anyone in the class spots it.

As a final exercise how about thinking about what other fantastic properties Wau has?

This links really well with the ToK question about where do we get our knowledge from – does the authority of mathematics or science allow people to be mislead more easily? A good example (in a similar vein to Wau is the “health scare” about Dihydrogen Monoxide (DHMO).


From the website DHMO:

Dihydrogen Monoxide (DHMO) is a colorless and odorless chemical compound. The atomic components of DHMO are found in a number of caustic, explosive and poisonous compounds such as Sulfuric Acid, Nitroglycerine and Ethyl Alcohol.

Each year, Dihydrogen Monoxide is a known causative component in many thousands of deaths and is a major contributor to millions upon millions of dollars in damage to property and the environment. Some of the known perils of Dihydrogen Monoxide are:
1) Death due to accidental inhalation of DHMO, even in small quantities.
2) Prolonged exposure to solid DHMO causes severe tissue damage.
3) Excessive ingestion produces a number of unpleasant though not typically life-threatening side-effects.
4) DHMO is a major component of acid rain.
5) Gaseous DHMO can cause severe burns.

Sounds pretty scary – and something that should be regulated. And indeed the website has been the cause of numerous petitions to MPs around the world demanding that it be banned. It is however an internet hoax. All the information is correct – it’s just that it refers to……water. People often have a deference to the authority of scientific or mathematical arguments – which can make them a very powerful tool in persuading people what to believe.

For anyone who wants to know what Wau is, the answer is below in white text (highlight to reveal!)

Wau is 1. Now watch the video again!

If you enjoyed this post you might also like:

Graham’s Number – literally big enough to collapse your head into a black hole – a post about an unimaginably big number.

e’s are good – He’s Leonard Euler. – A discussion about the amazing number e.


Cracking ISBN and Credit Card Codes

ISBN codes are used on all books published worldwide. It’s a very powerful and useful code, because it has been designed so that if you enter the wrong ISBN code the computer will immediately know – so that you don’t end up with the wrong book. There is lots of information stored in this number. The first numbers tell you which country published it, the next the identity of the publisher, then the book reference.

Here is how it works:

Look at the 10 digit ISBN number. The first digit is 1 so do 1×1. The second digit is 9 so do 2×9. The third digit is 3 so do 3×3. We do this all the way until 10×3. We then add all the totals together. If we have a proper ISBN number then we can divide this final number by 11. If we have made a mistake we can’t. This is a very important branch of coding called error detection and error correction. We can use it to still interpret codes even if there have been errors made.
If we do this for the barcode above we should get 286. 286/11 = 26 so we have a genuine barcode.

Check whether the following are ISBNs

1) 0-13165332-6
2) 0-1392-4191-4
3) 07-028761-4

Challenge (harder!) :The following ISBN code has a number missing, what is it?
1) 0-13-1?9139-9

Answers in white text at the bottom, highlight to reveal!

Credit cards use a different algorithm – but one based on the same principle – that if someone enters a digit incorrectly the computer can immediately know that this credit card does not exist.  This is obviously very important to prevent bank errors.  The method is a little more complicated than for the ISBN code and is given below from computing site Hacktrix:

creditcard2credit card 4creditcard3credit card 6credit card 5credit card 8credit card 7

credi card 9 You can download a worksheet for this method here. Try and use this algorithm to validate which of the following 3 numbers are genuine credit cards:

1) 5184 8204 5526 6425

2) 5184 8204 5526 6427

3) 5184 8204 5526 6424

Answers in white text at the bottom, highlight to reveal!

1) Yes
2) Yes
3) No
1) 3 – using x as the missing number we end up with 5x + 7 = 0 mod 11. So 5x = 4 mod 11. When x = 3 this is solved.
Credit Card: The second one is genuine

If you liked this post you may also like:

NASA, Aliens and Binary Codes from the Stars – a discussion about how pictures can be transmitted across millions of miles using binary strings.

Cracking Codes Lesson – an example of 2 double period lessons on code breaking

NASA, Aliens and Binary Codes from the Star

The Drake Equation was intended by astronomer Frank Drake to spark a dialogue about the odds of intelligent life on other planets. He was one of the founding members of SETI – the Search for Extra Terrestrial Intelligence – which has spent the past 50 years scanning the stars looking for signals that could be messages from other civilisations.

In the following video, Carl Sagan explains about the Drake Equation:

The Drake equation is:


N = the number of civilizations in our galaxy with which communication might be possible (i.e. which are on our current past light cone);
R* = the average number of star formation per year in our galaxy
fp = the fraction of those stars that have planets
ne = the average number of planets that can potentially support life per star that has planets
fl = the fraction of planets that could support life that actually develop life at some point
fi = the fraction of planets with life that actually go on to develop intelligent life (civilizations)
fc = the fraction of civilizations that develop a technology that releases detectable signs of their existence into space
L = the length of time for which such civilizations release detectable signals into space

The desire to encode and decode messages is a very important branch of mathematics – with direct application to all digital communications – from mobile phones to TVs and the internet.

All data content can be encoded using binary strings. A very simple code could be to have 1 signify “black” and 0 to signify “white” – and then this could then be used to send a picture. Data strings can be sent which are the product of 2 primes – so that the recipient can know the dimensions of the rectangle in which to fill in the colours.

If this sounds complicated, an example from the excellent Maths Illuminated handout on codes:


If this mystery message was received from space, how could we interpret it? Well, we would start by noticing that it is 77 digits long – which is the product of 2 prime numbers, 7 and 11. Prime numbers are universal and so we would expect any advanced civilisation to know about their properties. This gives us either a 7×11 or 11×7 rectangular grid to fill in. By trying both possibilities we see that an 11×7 grid gives the message below.


More examples can be downloaded from the Maths Illuminated section on Primes (go to the facilitator pdf).

A puzzle to try:

“If the following message was received from outer space, what would we conjecture that the aliens sending it looked like?”

0011000 0011000 1111111 1011001 0011001 0111100 0100100 0100100 0100100 1100110

Hint: also 77 digits long.

This is an excellent example of the universality of mathematics in communicating across all languages and indeed species. Prime strings and binary represent an excellent means of communicating data that all advanced civilisations would easily understand.

Answer in white text below (highlight to read)

Arrange the code into a rectangular array – ie a 11 rows by 7 columns rectangle. The first 7 numbers represent the 7 boxes in the first row etc. A 0 represents white and 1 represents black. Filling in the boxes and we end up with an alien with 2 arms and 2 legs – though with one arm longer than the other!
If you enjoyed this post you may also like:

Cracking Codes Lesson – a double period lesson on using and breaking codes

Cracking ISBN and Credit Card Codes– the mathematics behind ISBN codes and credit card codes

Benford’s Law – Using Maths to Catch Fraudsters

Benford’s Law is a very powerful and counter-intuitive mathematical rule which determines the distribution of leading digits (ie the first digit in any number).  You would probably expect that distribution would be equal – that a number 9 occurs as often as a number 1.  But this, whilst intuitive, is false for a large number of datasets.   Accountants looking for fraudulant activity and investigators looking for falsified data use Benford’s Law to catch criminals.

The probability function for Benford’s Law is:

benford 5


This clearly shows that a 1 is by far the most likely number to occur – and that you have nearly a 60% chance of the leading digit being 3,2 or 1.   Any criminal trying to make up data who didn’t know this law would be easily caught out.

Scenario for students 1:

You are a corrupt bank manager who is secretly writing cheques to your own account.  You can write any cheques for any amount – but you want it to appear natural so as not to arouse suspicion.  Write yourself 20 cheque amounts.  Try not to get caught!

Look at the following fraudualent cheques that were written by an Arizona manager – can you see why he was caught?   


Scenario for students 2:

Use the formula for the probability density function to find the probability of the respective leading digits.  Look at the leading digits for the first 50 Fibonacci numbers.  Does the law hold?

benford 4

There is also an excellent Numberphile video on Benford’s Law.  Wikipedia has a lot more on the topic, as have the Journal of Accountancy.

If you enjoyed this topic you might also like:

Amanda Knox and Bad Maths in Courts – some other examples of mathematics and the criminal justice system.

Cesaro Summation: Does 1 – 1 + 1 – 1 … = 1/2? – another surprising mathematical result.

traffic simulation

Simulations -Traffic Jams and Asteroid Impacts

This is a really good online Java app which has been designed by a German mathematician to study the mathematics behind traffic flow.  Why do traffic jams form?  How does the speed limit or traffic lights or the number of lorries on the road affect road conditions?   You can run a number of different simulations – looking at ring road traffic, lane closures and how robust the system is by applying an unexpected perturbation (like an erratic driver).

There is a lot of scope for investigation – with some prompts on the site.  For example, just looking at one variable – the speed limit – what happens in the lane closure model?  Interestingly, with a homogenous speed of 80 km/h there is no traffic congestion – but if the speed is increased to 140km/h then large congestion builds up quickly as cars are unable to change lanes.   This is why reduced speed limits  are applied on motorways during lane closures.

Another investigation is looking at how the style of driving affects the models.  You can change the politeness of the drivers – do they change lanes recklessly?  How many perturbations (erratic incidents) do you need to add to the simulation to cause a traffic jam?

This is a really good example of mathematics used in a real life context – and also provides some good opportunities for a computer based investigation looking at the altering one parameter at a time to note the consequences.


Another good simulation is on the Impact: Earth page.  This allows you to investigate the consequences of various asteroid impacts on Earth – choosing from different parameters such as diameter, velocity, density and angle of impact.  It then shows a detailed breakdown of thee consequences – such as crater size and energy released.   You can also model some famous impacts from history and see their effects.   Lots of scope for mathematical modelling – and also for links with physics.  Also possible discussion re the logarithmic Richter scale – why is this useful?

Student Handout

Asteroid Impact – Why is this important?
Comets and asteroids impact with Earth all the time – but most are so small that we don’t even notice. On a cosmic scale however, the Earth has seen some massive impacts – which were they to happen again today could wipe out civilisation as we know it.

The website Impact Earth allows us to model what would happen if a comet or asteroid hit us again. Jay Melosh professor of Physics and Earth Science says that we can expect “fairly large” impact events about every century. The last major one was in Tunguska Siberia in 1908 – which flattened an estimated 80 million trees over an area of 2000 square km. The force unleashed has been compared to around 1000 Hiroshima nuclear bombs. Luckily this impact was in one of the remotest places on Earth – had the impact been near a large city the effects could be catastrophic.

Jay says that, ”The biggest threat in our near future is the asteroid Apophis, which has a small chance of striking the Earth in 2036. It is about one-third of a mile in diameter.”

Task 1: Watch the above video on a large asteroid impact – make some notes.

Task 2:Research about Apophis – including the dimensions and likely speed of the asteroid and probability of collision. Use this data to enter into the Impact Earth simulation and predict the damage that this asteroid could do.

Task 3: Investigate the Tunguska Event. When did it happen? What was its diameter? Likely speed? Use the data to model this collision on the Impact Earth Simulation. Additional: What are the possible theories about Tunguska? Was it a comet? Asteroid? Death Ray?

Task 4: Conduct your own investigation on the Impact Earth Website into what factors affect the size of craters left by impacts. To do this you need to change one variable and keep all the the other variables constant.  The most interesting one to explore is the angle of impact.  Keep everything else the same and see what happens to the crater size as the angle changes from 10 degrees to 90 degrees.  What angle would you expect to cause the most damage?  Were you correct?  Plot the results as a graph.

If you enjoyed this post you might also like:

Champagne Supernovas and the Birth of the Universe – some amazing photos from space.

Fractals, Mandelbrot and the Koch Snowflake – using maths to model infinite patterns.

pigeon maths

Even Pigeons Can Do Maths

This is a really interesting study from a couple of years ago, which shows that even pigeons can deal with numbers as abstract quantities – in the study the pigeons counted groups of objects in their head and then classified the groups in terms of size. From the New York Times Article:

“Given groups of six and nine, they could pick, or peck, the images in the right order. This is one more bit of evidence of how smart birds really are, and it is intriguing because the pigeons’ performance was so similar to the monkeys’. “I was surprised,” Dr. Scarf said.

He and his colleagues wrote that the common ability to learn rules about numbers is an example either of different groups — birds and primates, in this case — evolving these abilities separately, or of both pigeons and primates using an ability that was already present in their last common ancestor.

That would really be something, because the common ancestor of pigeons and primates would have been alive around 300 million years ago, before dinosaurs and mammals. It may be that counting was already important, but Dr. Scarf said that if he had to guess, he would lean toward the idea that the numerical ability he tested evolved separately. “I can definitely see why both monkeys and pigeons could profit from this ability,” he said.”

To find mathematical ability amongst both monkeys and pigeons therefore raises two equally interesting possibilities.  Perhaps basic numeracy is a rare trait, but such a fundamentally important skill for life that it emerged  hundreds of millions of years ago.  Or perhaps basic numeracy is a relatively common trait – which can evolve independently in different species.

Either way, it is clear that there must be an evolutionary benefit for being able to process abstract quantities – most likely in terms of food.  A monkey who can look at two piles of coconuts and count 5 in one pile and 6 in the other and know that 6 is a bigger quantity than 5 can then choose the larger pile to sit alongside and eat.   Perhaps this evolutionary benefit is the true origin of our ability to do maths.

Another similar experiment looked at the ability of chimpanzees to both count numbers, and also demonstrated their remarkable photographic memory.

On the screen the monkeys are given a flash of 10 number for a fraction of a second, before the numbers are covered up, and they then proceed to correctly show the position of all numbers from 1-10.  They are much better at this task than humans.  This is a good task to try at school using the online game here  and would also make a good IB investigation.   Can you beat the chimps?

This all ties into the question about where mathematical ability comes from. If there had been no evolutionary ability for such abstract abilities with numbers, then perhaps today our brains would be physically incapable of higher level mathematical thinking.

If you enjoyed this post you might also like:

Does it Pay to be Nice? Game Theory and Evolution

Langton’s Ant – Order out of Chaos

A maths song sung by current flavour of the month One Direction – follow the lyrics to arrive at the total.

Some of the best maths songs are by Learning Upgrade, such as, videos on circle formulae, fractions, exponents, the quadratic formula and the one below, “Mean, Median and Mode”:

Some other good maths songs:

Westerville South High School in Ohio have made some great rap-based maths songs such as the trigonmentry song, Getting Triggy With It  

The Calculus Rhapsody is a fantastic  take on Queen’s famous song – and good for IB SL and HL students.

And James Blunt’s Triangle is good for a KS3 shape and space introduction. 


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