THE LESSON ROOM
A little prediction
A folded prediction and some friendly arithmetic. Begin here: your hands can relax while your words do the work.
WHAT YOUR AUDIENCE SEES
The effect
You leave a prediction in view. A friend starts with a number of their own, follows a few instructions, and arrives at your prediction.
What you need
- Paper and a pencil
- An envelope or a folded piece of paper
Your practice goal
Give the instructions clearly enough that a friend can follow without asking you to repeat.
I’m here to learn. Show me the method.
Method
Before you begin, write 5 on paper, fold it, and leave it in view. Ask your friend to choose a whole number from 1 to 20 and keep it to themselves.
Give these instructions one at a time:
- Double your number.
- Add 10.
- Divide the total by 2.
- Subtract the number you first thought of.
Ask them to say their final answer, then have them open the prediction. The answer is always 5: starting with x gives (2x + 10) ÷ 2 − x = 5.
Check with 7: 14, 24, 12, then 5. Check with 16: 32, 42, 21, then 5.
Performance and patter
Frame this as a playful prediction, not real mind reading: “We’ll take different roads and see if we reach the same destination.” Pause between instructions. Offer paper or a calculator so the experience is about surprise, not a test of mental arithmetic.
Common mistakes
- Giving the whole sequence too quickly.
- Saying “subtract your number” without specifying the starting number.
- Opening the prediction before the spectator says the result.
- Repeating it immediately with the same ending. Finish while the surprise is fresh.
Make it yours
Choose a different ending by changing the amount added. Adding 14 makes the ending 7. Test every change privately and write the matching prediction before you perform.
Original presentation using elementary algebra; no commercial routine is reproduced.
Share the effect, respect the creator, and let people choose whether to learn. Our code →