Been to right brain last year, so I only attended the mental arithmetic ones. Read my review on right brain here.
I was introduced by my dad to mental arithmetic class when I was in Standard 3. He sent me to UC Mas a tad bit too late because I was so used of the old method and thought my congak was so much faster than mental arithmetic.
I was one of the best; if not the best math student in my school. Inherited it from my dad, so congak became a nature to me. I lost interest in mental arithmetic which caused me to skip tuition and spent my two hours in playground having Maggi Ayam instant with my friend instead.
Dear Allah, please let my daughters be so much better than me.
Anyhow, I have always thought mental arithmetic is useful. Was sooo happy attending the class with Puan Lina's aura; please please please go. I had so much fun.
Having said that, let me give you an overview on how to introduce mental arithmetic for your kids.
You need an abacus; train them with abacus first before they can do mental arithmetic.
The most common abacus is split into two basic rows:
the top row for the "5"s, and
the bottom row for the "ones".
Use index finger to slide the top rows and your thumb to slide the bottom rows.
I will update the next step. Till then, doakan for the strength for me to write more often!