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Welcome to the March 2015 edition of the Transum Mathematics Newsletter. This month the focus is on probability and the puzzle for this month is one that all Maths teachers will probably (?) know the answer to. What is the minimum number of pupils there needs to be in a class such that the probability of two or more of them having the same birthday is greater than a half? If you don’t know have a guess (make an estimate).

The answer is at the end of this newsletter but for now let’s look at what was new or updated on the Transum website last month.

The copyright holders of the puzzles Suko and Sujiko granted Transum permission to create versions of the puzzles online. The Transum version allows the user to have up to 5 clues to help find the solution. This allows the puzzles to be used with classes of different abilities as the teacher can decide just how difficult each puzzle should be.

Beat the Clock is great fun no matter how good your numeracy skills are. Race to answer the mental arithmetic questions as a curtain slowly lowers concealing the questions on the screen. There are nine levels of difficulty but you can make the challenge easier by choosing to only answer the questions in the left column.

Assuming your school does not have a policy of using traditional playing cards in the classroom you’ll find they are a versatile resource for mathematical activities. Visit the new Playing Card Maths section of the website to see all the ideas that have been gathered together so far. Please get in tough if you have any other suggestions. If you are a one-to-one Maths Tutor you may want to always have a pack of cards in your bag as a plan ‘B’ just in case the other activities you have planned for the tutorial go horribly wrong.

If you are interested in times table skills I’m sure you are aware of one of the most popular Transum activities called TablesMaster. Now when you claim your trophy for completing an exercise you have the option to view your very own ‘reverse bar chart’, comparing your trophy winning times for each of the times tables. It has proved to be a great motivator for pupils working on their times tables.

Other less newsworthy activities have been added to the site and many updated but you’ll probably come across those when you browse the topic index.

Probability is a unique topic in the school mathematics syllabus. As well as learning the techniques, formulas and procedures pupils should develop a ‘feel’ for what probability means. Most adults have a limited understanding of the concept and would think that if they had tossed a coin nine times and it had landed heads each time that the probability of the tenth toss landing tails is more likely as it hasn’t happened for so long! So does the coin have a memory? Does it know that if it has landed heads many times that it should be time to give tails a chance? No of course not. The probability is still 50% (unless the coin is biased in some way).

There are some nice examples of probability in the real world I have just been listening to on the excellent podcast called ‘No Such Thing As A Fish’. The QI Elves tell of how Spotify changed its random play list because people didn’t think it really was random enough! You can hear that excerpt as part of the Transum Podcast for this month.

The surprising answer to this month's question is that there need only be 23 pupils for the probability of two or more of them to have the same birthday to be greater than a half! The reason is well documented on the web and in particular in an article called ‘The Birthday Problem’ on Wikipedia. If you’d like to try to prove it yourself you may want to consider the question of the birthdays **not** being on the same day and subtract your result from one. Good Luck.

John

ps 3.14% of Sailors are PI rates!

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