Classroom Number Tricks

Magic Maths

Maths Workshop

Maths Workshop

Here is an exercise you could incorporate into a maths lesson to add interest and fire up the children’s imaginations. Tell your class you are going to teach them a magic trick using numbers.

Number trick : using the number 8

You will need calculators and a white board. This is the number sequence we will be using:

1 x 8 + 1 = 9

12 x 8 + 2 = 98

123 x 8 + 3 = 987

1234 x 8 + 4 = 9876

12345 x 8 + 5 = 98765

123456 x 8 + 6 = 987654

1234567 x 8 + 7 = 9876543

12345678 x 8 + 8 = 98765432

123456789 x 8 + 9 = 987654321

 

To explore how the trick works start by writing down the first two calculations:

1 x 8 + 1 =

12 x 8 + 2 =

but don’t show the answers yet.

Let the children work out the number sequence and have them tell you what the next row will be.

 

Keep going until you have this:

1 x 8 + 1 =

12 x 8 + 2 =

123 x 8 + 3 =

1234 x 8 + 4 =

12345 x 8 + 5 =

123456 x 8 + 6 =

1234567 x 8 + 7 =

12345678 x 8 + 8 =

123456789 x 8 + 9 =

 

Now let the children use their calculators to find the answer to the last two sums. When they have done so, write them down and be sure to keep the digits vertically aligned.

1 x 8 + 1 =

12 x 8 + 2 =

123 x 8 + 3 =

1234 x 8 + 4 =

12345 x 8 + 5 =

123456 x 8 + 6 =

1234567 x 8 + 7 =

12345678 x 8 + 8 = 98765432

123456789 x 8 + 9 = 987654321

Ask if they can see a pattern.

Ask how many numbers are in each answer.

Now have them write down what they think the remaining answers will be and then check them on their calculators.

 

Using their newly acquired knowledge the children are now ready to become classroom magicians. Here is how you can turn the trick into your own amazing maths magic show.

 

Performance

Choose a child to be the magician.

The magician declares that he / she has amazing maths skills and can predict the answers of difficult sums using his / her extraordinary powers.

The magician picks a member of the audience and gives them a calculator. Next she asks them to pick a number sequence beginning with 123. It can be any sequence up to the number nine ie 123456789. Then the spectator is asked to multiply by 8 and finally add x ( where x is the last number in the sequence ).

Example: If the spectator chose 1234 the the magician tells them to multiply be eight and add four ( x  =  4 )

The magician then declares the answer to the amazement of all. ( He / she simply counts down from nine ie if x was six the answer would be 987654 ) and takes a bow.

Big round of applause!

 

Book a Magic Maths Workshop for your school. Find out more by going to Maths Workshop Day.

 

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