How should you practise addition and subtraction mental math after learning the shortcuts?

Do short sets of actual calculations: solve first, reveal the card, compare your route, then rate based on accuracy and effort.

Use the flashcards like a gym set:

1. Pick a small target — 10 additions/subtractions, not an endless session.
2. Say the answer before revealing — no paper, no calculator, no half-checking.
3. Reveal and compare routes — if your answer is right but your route was clumsy, still learn the cleaner route.
4. Rate honestly — Easy if it was instant, Good if correct with effort, Hard if slow or fragile, Again if wrong.
5. Log the mistake type — sign error, bad compensation direction, lost running total, or arithmetic slip.

The goal is not to memorise these exact numbers. The goal is to make the pattern automatic: round, adjust, balance, count up, or run left-to-right without having to decide slowly.