OK, Ari, what is 567 times 123? And you have exactly three seconds to answer, so you better move fast. SHAPIRO: You can't be serious right now, Juana. SUMMERS: (Laughter). SHAPIRO: There's no way ...

Ever dreamt of solving math problems in your head with the speed of a calculator? Mental math might seem challenging, but it's a skill attainable through the right tools and techniques. The abacus, an ...