Start by writing the number 1089 on a piece of paper and put it in your pocket. Now get someone to choose a three digit number where the last digit is at least 2 less than the first digit. Turn it round to form a new three digit number, then subtract it from the first one. For example, 481 − 184 = 297. Now turn the new number round to form a fourth three digit number, and add it to the third. 297 + ...

## Hypothesis testing made easy

Carrying out a hypothesis test often causes confusion. Here's how it works. Some hypothesis tests start with a known fact, such as "25% of patients treated for a particular disease will suffer side effects." A drug company may then claim that "a new treatment reduces the number of patients suffering side effects." The original figure, the status quo, is known as the "null hypothesis" and given the symbol H0. The new claim is called the "alternative hypothesis" and given the symbol ...

## Does division by zero = infinity?

Why should it? Well, try this: 5 ÷ 10 = 0.55 ÷ 1 = 55 ÷ 0.1 = 505 ÷ 0.01 = 5005 ÷ 0.001 = 5000 As we divide by smaller and smaller numbers the result gets ever bigger. Logically, then, as the divisor tends to (ie gets closer to) zero, so the result tends to infinity. But this is not the same as saying that division by zero actually is infinity, is it? What about drawing a graph with ...

## A Mathematical Card Trick

Card tricks fall into several categories, and my favourite are those which look amazing but actually have some pretty simple maths behind them. Here's one of the simplest! 1. Take an ordinary pack of cards and shuffle it. Deal out 26 cards, face up, and remember the 7th card. 2. When you've dealt out the 26 cards, pick up the pile and turn them face down on the table, to one side. (If you're brave, shuffle them first, but make ...

## Ancient Babylonians Do It Again!

Babylon – in ancient Mesopotamia, now Iraq – hosted one of the earliest recorded civilisations. Partly because they became a trading nation, they developed some of the earliest mathematical techniques. We already know that they were aware of what we now call Pythagoras' Theorem (in a numeric sense, since algebra didn't exist), but the some of the secrets of a tablet known as Plimpton 322 have been unravelled to show that they had developed a highly sophisticated form of trigonometry, ...

## Sampling Methods

In statistics, a population is the complete set of data which is to be analysed. A population may consist of people (e.g. those living in a particular city), or living things (e.g. the population of all humpback whales), but could be any set of objects with something in common (e.g. all cars travelling on a particular road in a 24 hour period). Usually, it isn't possible to analyse a complete population. Why? It would take too long It would be too ...

## Sam Lloyd, Master of Puzzles

Sam Lloyd was born in Philadelphia in 1841, but lived most of his life in New York. He was primarily a chess player and composer of chess problems, but he also delighted in mathematical puzzling. Actually, not just mathematical puzzles, but word puzzles; picture puzzles; tangrams; he composed thousands of them. In fact, it was one of his pictorial puzzles which grabbed my attention at a very early age, and possibly sparked my enjoyment of such puzzles. Have a look ...

## Help with your IB Mathematics

Whether you are in the first weeks of your diploma course, or whether you are halfway through, there are always going to be some parts of the maths syllabus that make you scratch your head! Over the past couple of years some of the blogs I have written have concentrated on specific topics which I know can benefit from further explanation. I thought it would be helpful to list those blogs here: a reference for those that are new to ...

## Games with Dots

Do people still play pencil and paper games these days? I grew up with them in my family – all sorts from number games, word games, drawing games. A number of the mathematical games involve spots or dots and, believe me, they can be fiendishly difficult to win against a good opponent. The simplest of all is boxes. A square grid of dots is created (the bigger you make it, the longer the game). The first player joins two adjacent dots with either ...

## MacTutor History of Mathematics

In my wanderings around the internet I came across a superb resource for anyone interested in, or needing information about, mathematicians, the history of mathematics, mathematical chronologies – even a 'famous curves' index. This is the MacTutor History of Mathematics site, created by John J. O'Connor and Edmund F. Robertson of the University of St. Andrews in Scotland. Under 'Mathematicians of the Day' there's an index of those who were born or died on every day of the year. I'm amazed ...