The Pick the Numbers Trick
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Perform a number prediction magic trick where you guide someone to pick numbers, do simple operations, and confidently reveal the hidden result.

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Step-by-step guide to perform the Pick the Numbers Trick

What you need
Eraser, paper, pencil, small scrap of paper for prediction

Step 1

Write the number 4 on the small scrap of paper.

Step 2

Fold the scrap so the 4 is hidden.

Step 3

Put the folded scrap face down on the table.

Step 4

Ask a friend to think of any whole number between 1 and 100.

Step 5

Tell your friend to keep that number secret and remember it.

Step 6

Ask your friend to double their number by multiplying it by 2.

Step 7

Tell your friend to add 8 to the doubled number.

Step 8

Ask your friend to divide the new total by 2.

Step 9

Tell your friend to subtract their original number from that result and keep the final number secret.

Step 10

Open the folded scrap to reveal your prediction.

Step 11

Ask your friend if their secret result is 4 and celebrate the surprise.

Step 12

Share your finished magic trick on DIY.org

Final steps

You're almost there! Complete all the steps, bring your creation to life, post it, and conquer the challenge!

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Help!?

What can we use instead of a small scrap of paper if we don't have one?

Use a folded sticky note, business card, or torn notebook paper to 'Write the number 4' and 'Fold the scrap so the 4 is hidden' exactly like the instructions.

What if my friend gets the arithmetic wrong or forgets their original number during the steps?

Have them say each instruction aloud while you guide them through 'double your number,' 'add 8,' 'divide by 2,' and 'subtract your original number,' or let them use a calculator so the final secret will still be 4 when you 'Open the folded scrap to reveal your prediction.'

How can I adapt the trick for younger or older kids?

For younger kids use counters or fingers to demonstrate 'double their number,' 'add 8,' and 'divide by 2,' and for older kids let them swap the 'add 8' step for a different even number and predict the new result before you open the scrap.

How can we make the trick more impressive or personalized?

Decorate the 'small scrap of paper' with stickers, film your performance to 'Share your finished magic trick on DIY.org,' or change the 'add 8' step to another even number and write that new predicted result on the folded scrap for a custom reveal.

Watch videos on how to perform the Pick the Numbers Trick

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Guess the numbers from 1 to 100 - Learn to read and write numbers from 1 to 100

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Facts about number tricks and mental math

♟️ The ancient Lo Shu magic square (China) is a 3×3 grid where every row, column, and diagonal adds up to 15.

🔢 Classic trick formula — pick a number, double it, add 10, halve it, subtract the original number — you'll always end up with 5!

🎩 Famous mentalists like Derren Brown mix psychology and showmanship, but lots of impressive-looking effects are pure math.

🧠 Many number-prediction tricks are "self-working": clever algebra makes the answer predictable no matter the starting number.

🧮 Young children can follow these tricks easily because they only need basic operations: +, −, ×, and ÷.

How do I perform the Pick the Numbers Trick so I can always predict the result?

Ask a volunteer to choose any whole number (not zero) and multiply it by 9. Have them sum the digits of the product; if the result has more than one digit, repeat summing until a single digit remains. Dramatically reveal that you predicted the final single digit will be 9. For showmanship, write a sealed prediction beforehand and unveil it after they finish. Practice clear instructions and pacing.

What materials do I need for the Pick the Numbers Trick?

No special materials are required—just a volunteer and basic arithmetic. Optional items: paper and pencil so the child can show their multiplication and digit sums, an envelope or index card to hide a written prediction, and a small notepad for notes. These props add theatre but aren’t necessary for the math to work.

What ages is the Pick the Numbers Trick suitable for?

Suitable for children about 6 years and older who can multiply and add digits; younger kids can join with adult help. Ages 6–9 often need guidance and paper to track steps. Ages 10+ can perform confidently, practice presentation, and learn to disguise the method. Supervise early learners and encourage them to explain steps to reinforce arithmetic and build confidence.

What are the benefits, safety tips, or variations of the Pick the Numbers Trick?

Benefits include improved mental math, pattern recognition, and presentation skills; it builds curiosity about number rules. Safety is simple—no hazardous materials—just supervise for frustration with numbers. Variations: use the classic multiply-by-9 digit-sum reveal, or try other predictable operations and reveal methods. Add storytelling, a sealed prediction, or audience participation to increase drama and engagement.
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The Pick the Numbers Trick. Activities for Kids.