Inside History on Instagram: "Imagine a young child solving ten massive five-digit numbers in just 8 seconds—without a calculator, and without even touching a physical abacus. That’s the astonishing power of the Mental Abacus! This technique trains children to visualize an abacus in their minds, allowing them to perform complex arithmetic at lightning speed. The results are nothing short of incredible. Take Japan’s Flash Anzan championship, for example: champion Takeo Sasano added fifteen three-