Memory when it comes to math is kinda different I think. I’ve been familiar with the tables, been able to give the answer just by looking at it. Since I’m often exposed to numbers as a student. It’ll be hard at first but you have to practice.
Here are some of my book recommendations that may help you:
•How To Learn And Memorize Math, Numbers, Equations, And Simple Arithmetic (Magnetic Memory Series) by Anthony Metivier
•Secrets on Mental Math by Arthur Benjamin and
•Maths Sutra by Gaurav Tekriwal
•Speed Mathematics Simplified by Edward Stoddard
(THERE ARE A LOT OF OTHER BOOK RECOMMENDATIONS IN THE FORUM, SORRY CAN’T PROVIDE THE LINK BUT IT’S EASY TO SEARCH UP)
Mostly this book has exercises so you could try them out, and train by yourself.
There are a lot of methods in Mental Math, and I’m learning different methods so I get used to them and when I see a problem I could automatically choose an appropriate method.
I’m learning Vedic Maths, Trachtenberg System, and I also have an abacus, (I use abacus mostly on addition) I’m still practicing on multplication.
But it’s up to you, and don’t assume that you’ll see the results real fast. It takes a lot of practice so devote some of your time for learning the methods. At first it is hard, since the brain is unfamiliar yet, but over time it’ll be worth it.