About ShowMath

The idea: perform, don’t just practise

Nobody rehearses like someone with a show on Friday. ShowMath treats mental math as a performance skill: you learn a self-working trick, then perform it to a real person. The trick does the magic — but a smooth performer has done the mental arithmetic many times, which is the practice hiding inside the fun.

The maths is real

• Any-Day uses the Doomsday method — clock-style “mod 7” arithmetic to find the weekday of any date.
• The Missing Digit is casting out nines — the number-theory fact that a number and its digit sum leave the same remainder mod 9.
• ×11 and squares ending in 5 are place-value identities you can see and prove, not memorised gimmicks.

Honest promise

ShowMath is built to make practice motivating and give you something to show off. It is not a claim to make you a genius, and performing a self-working trick isn’t the same as deep mastery — it’s a doorway to it. Drill the arithmetic at MentalForge.

Your privacy

Everything runs on your device. There are no accounts, no timers, no streaks, and no data — not a birthday, not a number — ever leaves your phone. Whatever a volunteer types in Show Mode is used for that one reveal and then forgotten.

Credit

The performance-first approach to mental math is inspired by the work of mathematician and “mathemagician” Arthur Benjamin. ShowMath’s routines, patter, and examples are our own.