Archive for the ‘Arithmetic’ Category


Trick 2: The Math Teacher Knows

August 4, 2018


The Math Teacher Knows Everything

Requirements: 1 die, a fanfare would be nice.

You will find a fanfare here.

Ask a student to roll the die, double the number and add 5.  He can show the class the number, but not you.

Ask the student to multiply this number by 5.

Ask the student to roll the die again and add this number to the total.

Now you can tell them the numbers they rolled.


N1 = 3

Double: 2N1 = 6

Add 5: 2N1 + 5 = 11

x5:   5(2N1 + 5) = 55

Roll dice:

N2 = 4

Add 4:

55 + 4 = 59

The Math Teacher Knows:

Secretly subtracts 25 from this number:

59 – 25 = 34

Da! Da! There are the two numbers rolled.

Source: Magic/Menatalism Tips and Tricks


Awesome Lego Maths and a Giant Lego Tree

July 28, 2018

You may not want Lego brick blossoms falling on your head,

but the Giant Lego Cherry Blossom tree has some awesome maths

to explore. See the tree built in fast forward below.


Trick 3: Maths Swami Knows Your Age and Foot Size

July 9, 2018

Maths Swami 1: A Magic No.

Maths Swami 2: I Know Your Birthday

Requirements: Calculator and spooky demeanor

Imagine your birthday was 24 September 1973.

Written as an American date (not UK or Australia) this would be:


Give the calculator to a student:

Take birthday month and add 18:

9 + 18 = 27

x 25

27 x 25 = 675

– 333

675 – 333 = 342

x 8

342 x 8 = 2736

– 554

2736 – 554 = 2182

Divide by 2

2182/2 = 1091

Add day of birthday date

1091 + 24 = 1115


1115 x 5 = 5575

+ 692

5575 + 692 = 6267

x 20

6267 x 20 = 125340

Add the last two digits only of your birth year

125340 + 73 = 125413

– 32940

125413 – 32940 = 92473 = 9-24-73

Yes! Yes!

Hint: It probably would be easier to ask them for their birthday. Ha! But Maths Swami’s are mysterious beings.

You will find a video link on Youtube


Trick 4: How to be a Mathematical Clairvoyant

June 22, 2018

How to be a Mathematical Clairvoyant

Requirements: Spooky music and spooky look.

You will find some spooky music here.

Tell your students you will beat them  adding up 5 x 5 digit numbers in your head when they are using calculators.


1. Ask a student to write down 2 x 5-digit numbers on the board.

2. You rapidly write a 5-digit number underneath.

3. Ask another student to write another 5-digit number.

4. You write another 5-digit number quickly.

5. You have 5 by 5 digit numbers. Say ‘Go’. You instantly write down the answer.

Stand back.

This is how it works:

N1 = 97413

N2 = 28619

N3 = 71380  (Each digit in N3 that you write down must add up to 9 with digits in No. above)

N4 = 64231

N5 = 35768  (Once again each digit in N5 must add up to 9 with digits above)

Now you will instantly write down the sum of these five numbers as


Da! DA!

The trick is to subtract 2 from N1 and put it in front:

N1 = 97413

N1 -2 = 97411

Sum of 5 numbers = 297411

This is why it works:

Hint: When you get your students to add up the five 5-digit numbers on a calculator you will beat them, but they will also get many different answers as a number of students will key incorrect numbers.

Magic Chat




Learning Jump Strategy from a Young Mathematician

June 8, 2018

Mathpig just learnt this from a young Mathematician age 9.

It is a great way to do maths because you are thinking ‘Mmmm! How can I work these numbers.’

Getting maths students to think about what they are doing is so much better than just having them guess ‘ Arrrr!  Whatever. Click B.’

More jump strategy information here.

This will be very useful later when it comes to a similar method used to simplify long division:


Trick 7: My Math Teacher is Psycho … Psychic!

May 17, 2018

Math Teacher Goes Psycho  ….  Psychic!

Requirements: Pack of cards and a little practise.

Watch this video to learn the trick. Then try it out on the class.

Beginner Math Prediction Card Trick


Trick 8: Spooky Maths Magic

May 4, 2018

Spooky Maths Magic

Requirements; Smart board/data projector.

 This is mental maths, but not hard maths. You can play this video by Marco Frezza  directly to the class.

It may not work on everybody, but it would be very interesting to see how many students are fooled by this spooky magic man.