Don't just settle for 'bad at math.' A teacher's eye for identifying a child's stumbling blocks

This child is bad at math.' At school, I sometimes hear words like these. But when I hear them, I want to ask one more ...

The story of how I became a genius with the abacus, and whether I can become a hero

Once I stepped into the world of the abacus, I became able to do mental arithmetic with 3-digit + 3-digit + 3-digit numbers.