Somebody names any number from 30 to 99. You draw a four-by-four grid and fill it in, fast, without stopping to think. Every row, every column, both diagonals and the four corners add up to their number.
✨ Level 2: Conjurer
⏱ 20 minutes to learn
🔮 Mind reading
🎒 Ages 10+
A bit of setting up, or ten to twenty minutes of practice.
What you need
The secret
Get ready, before anybody is watching
Learn the grid by heart: 1, 12, 7 in the top row; 11, 8, 2 in the second; 5, 10, 3 in the third; 4, 6, 9 in the bottom.
They don't hear your thoughts. Mind-reading tricks use maths that always lands on the same answer, a secret peek, or a code agreed with a partner beforehand. Magicians who do mind tricks are called mentalists.
The Instant Magic Square for kids: the whole trick
Somebody names any number from 30 to 99. You draw a four-by-four grid and fill it in, fast, without stopping to think. Every row, every column, both diagonals and the four corners add up to their number. It's a level 2 conjurer trick for ages 10 to 13 (grades 5th–7th), takes 20 minutes to learn, and needs 2 things you already have. Flick, the shop's rabbit, reads every step aloud with a picture, so a child can follow it alone.
The secret
Twelve of the sixteen boxes always hold the same small numbers. Only four boxes change, and each is their number minus 18, 19, 20 or 21.
What you need
A sheet of paper
A wooden pencil
Get ready, before anybody is watching
Learn the grid by heart: 1, 12, 7 in the top row; 11, 8, 2 in the second; 5, 10, 3 in the third; 4, 6, 9 in the bottom.
How to do it
Ask for any number from 30 to 99. Say they pick 50.
Draw a grid four boxes across and four boxes down on the paper.
Top row: their number minus 20, then 1, 12, 7.
Second row: 11, 8, their number minus 21, then 2.
Third row: 5, 10, 3, then their number minus 18.
Bottom row: 4, their number minus 19, then 6, 9.
Hand it over. Every row, column and diagonal adds to their number. Let them check!
Magic words to say
“Every number has a magic square hiding inside it. Most people never find theirs. Give me yours, and I'll draw it out for you before you can count to twenty.”
Pro tips
Work out the four changing numbers in your head first, while you draw the grid.
Fill the boxes in a jumbled order, not row by row. It looks much harder that way.
Show them the four corners and the middle four add up too. Most people never think to check those.
If something goes wrong
If a row doesn't add up, you've written a box wrong. Say "let me check my working", find the mistake, and fix it. Every real mathematician does that.
Safety notes
Only from the front.
No fire, no flames and nothing sharp in a child's hand anywhere in the Magic Shop. Nothing ever goes in a mouth, a nose or an ear.
Why it works
Each row, column and diagonal holds exactly one of the four changing boxes, plus fixed numbers that add up to the rest. The top row is (number − 20) + 1 + 12 + 7, and 1 + 12 + 7 is 20, so the row comes back to the number. Every other line works the same way.
What kind of trick is this?
🔮 Prediction. You knew all along, or you read their mind. Almost every trick ever invented is one of eight kinds, and knowing which one you're watching is how magicians work out how a new trick is done.
The skill it teaches:Practise like a pro. Ready means ten times in a row without looking at your hands. Perform it and it counts towards the Mind Reader badge.
Questions about the instant magic square
How do magicians read minds?
They don't hear your thoughts. Mind-reading tricks use maths that always lands on the same answer, a secret peek, or a code agreed with a partner beforehand. Magicians who do mind tricks are called mentalists.