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. They live in MentalForge’s Trick lab.

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.