Your secret settings

Your prediction

Write this on your prediction card before the trick.

Your number gets

Whole-number mode: press % and the screen shows something like × 7 (or ÷ 4). Tell them to multiply (or divide) by that. Press % again and it shows the add or subtract number, like + 123 or − 85. The app picks the whole number from 2 to 20 that leaves the smallest add.

This is what plain % does. You can also choose on the spot: press × then % for a multiply number, ÷ then % for a divide number, or + then % for add or subtract.

Multiply and divide numbers are usually long decimals (like 0.72386). Their calculator may end on something like 3,486.9999 instead of 3,487. Try it in Practice first.

How to use it

1. They add, subtract, multiply and divide whatever numbers they like on their calculator.
2. Get their running total onto this calculator. Either follow along and do the same steps here, or ask "what have you got so far?" and type it in.
3. Press %. The screen now shows your number.
4. Tell them to add that number (or multiply or divide, if that's what you chose). If an add number shows a minus sign, tell them to subtract it instead.
5. Their total now matches your prediction.

Giving your number in the middle (optional)

If they will do more steps after your number, list those steps here in order. You must decide these steps (for example "now double it, then add 10"). The app works backwards so they still land on your prediction.