Maths and magic
18 December 2009Add to My Folder
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Amaze your class with these ‘mathemagical’ tricks and teasers
Maths tricks can woo and wow children’s imaginations. They have a magical feel to them and can breathe mystery and fun into your classroom. This article contains a selection of tried and tested recreational activities to add a little zip to your maths teaching and inspire and deepen children’s interest. They offer a wide variety of classroom uses and are prime candidates for mathematical ‘milking’. Use them alongside formal maths teaching in starter and plenary sessions, within focus groups, as brain breaks or to end the day. They also provide excellent material for maths clubs.
It’s a good idea to start a file of your favourite tricks so you can use them year after year. Each time you introduce a new one to the class, give the children time to explore it and practise the maths for themselves. They can then prepare demonstrations to perform to you and the rest of the class.
- The number 11 sandwich
- Recurring number magic
- Postal number
- That’s original
- Number line magic
- The magic number
- Guess two nunbers
- A head full of numbers
1. The number 11 sandwich
A very neat trick for multiplying a two-digit number by 11 is to write down the number you are multiplying by, leaving a space between the two numbers. For example, to work out 35×11, leave a space between the 3 and 5 = 3_5. Now, add these two digits and place the answer in between. So 3 + 5 = 8, then place the 8 in between the 3 and 5 to make 385. Check this on a calculator to see that 35×11 is 385.
This method works if the total of the two digits is less than ten. If they add up to ten or more, you will need to add the 1 to the first digit and place just the second number in the space. For example, to do 67×11 you would separate the 6 and 7, add 6 and 7 to make 13, but rather than place 13 in between, place the 3 in the space and add the 1 to the 6, so the answer is 737.