I find (10x14) - (1x14) = 140 - 14 = 126 slightly quicker and less error prone than carrying the ten across the hundred boundary with 9x10 + 9x4 = 90 + 36 = 126

I find (10x14) - (1x14) = 140 - 14 = 126 slightly quicker and less error prone than carrying the ten across the hundred boundary with 9x10 + 9x4 = 90 + 36 = 126, I'm not an educator though so there may be better ways taught now. But this is wildly off topic, and in reality I'd rather someone knew how to use their calculator or excel or Python to do this sum than know how to do this sum in their heads. It's important they know the rough answer in terms of scale and shape, so that any mistype or error is quickly recognised, but I don't think it is important to actually know how to quickly do long multiplication in one's head.