Level 1 · Mind Tricks
Psychic Math
Ask anyone to think of a number, walk them through five steps, then reveal their answer before they tell you — and be right every time.
The Script
This trick works on a simple algebraic principle: the five steps are carefully chosen so that the volunteer's original number is completely cancelled out by step 5. The result is always the same constant — in this version, 6.
The Five Steps (what you say)
- "Think of any number."
- "Double it."
- "Add 12 to your result."
- "Divide by 2."
- "Subtract your original number."
"Your answer is… 6."
The Algebra Behind It
Let the volunteer's secret number be n. Tracking each step algebraically:
| Step | Instruction | Algebraic value |
|---|---|---|
| 1 | Think of n | n |
| 2 | Double it | 2n |
| 3 | Add 12 | 2n + 12 |
| 4 | Divide by 2 | n + 6 |
| 5 | Subtract original | (n + 6) − n = 6 ✓ |
At step 4, the result is n + 6 — the volunteer's number plus 6. Subtracting their original number in step 5 eliminates n entirely, leaving only 6. The 12 in step 3 divided by 2 in step 4 is the hidden constant that you predict.
Customising the Trick
You can force any answer simply by changing the number added in step 3. To predict k, use 2k in step 3. For example, to predict 10, say "add 20" instead of "add 12." The algebra always resolves to your chosen constant.
💡 Performance Tip
Use the sandbox's Performance Mode — the volunteer types their number without you seeing it, then tap "Reveal" to dramatically announce 6. The visual of a hidden input field makes it genuinely convincing even to adults who suspect a trick.