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&#x27;m not an educator though so there may be better ways taught now.<p>But this is wildly off topic, and in reality I&#x27;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.<p>It&#x27;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&#x27;t think it is important to actually know how to quickly do long multiplication in one&#x27;s head.