Head of the herd

9th March 2007 at 00:00
What's big, grey and makes pupils gasp? Patrick Allen shares his maths tricks

Danish elephants capture the imaginations of most children. As a supply teacher, I often need a strong opener to break the ice with a class, and here is how European pachyderms stroll to my rescue.

I ask the class to think of a number from 1 to 9 and multiply it by 10.

After subtracting their original number they must then add together the resulting digits. From this new number they subtract 5. Taking A as 1, B as 2, and so on they find the letter that corresponds to their number and think of a country beginning with that letter. Taking the second letter of that country they think of an animal, and from the first letter of the colour of that animal they must think of a fruit. Hey presto! The whole class is (usually) thinking of Danish elephants eating grapes.

While the maths here is rudimentary, forcing the children to arrive at the number 4 and, hence, the letter D, the outcome is nonetheless rewarding.

Clearly, this is not a trick I can use often in the same school without confronting herds of jaguars from Djibouti (although I applaud the efforts of a child who works that hard to catch me out). Happily I have other small wonders up my sleeve. Here is just one more: Write down any number of any length (say 3689015). Count the even digits in this number (including zeros) and write this total down (in 3689015 there are 3). Next to this number write the total number of odd digits in the original number (giving 34). Finally write down the total number of digits in the original number (giving 347). Repeat with this new number (347), writing EVEN, ODD and TOTAL to make a new number.

It is not long before you realise that number work is as easy as "1,2,3"

Patrick Allen is a maths supply teacher in junior schools in East Riding.

See more of his free primary teaching resources at www.classinaflash.co.uk

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