All my life I've done mental arithmetic the 'wrong way': I've calculated from left-to-right, instead of right-to-left. So when I do something like 24 + 35 I'll see the 50 first and then the 9 . This even applies when there's a carry and I'll do something like 36 + 56 as 80 + 12 . I do the same thing for multiplication as well. Turns out I'm not so weird after all (well, apart from the finding doing mental arithmetic fun bit). I've been reading Secrets of Mental Math: The Mathemagician's Guide to Lightning Calculation and Amazing Mental Math Tricks and the author, Michael Shermer, is just like me: he works from left-to-right. He, like me, has found this to be a good system because it lets you discard digits early and not hold some enormous calculation in your head. For example, in the calculation 124 + 353 you can immediately say "four hundred" before doing the rest of the sum. This seems to free up headspace (at least for m