We're overthinking. Think, instead, as a school marm with real chalk and a switch in hand, or even when kids used slate tablets: 10x is easy. 11x is easy up to

We're overthinking. Think, instead, as a school marm with real chalk and a switch in hand, or even when kids used slate tablets: 10x is easy. 11x is easy up to 10x. 12x requires a little work and pulls all the multiples together, but 13x just screws with everything we've learned so far. So, stop at 12. Or is a calculator in hand the default these days? As one who was proud to finally get to 12 x 12 = 144, I say make 'em suffer.