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   Mark Dominus (mjd@mathstodon.xyz)'s status on Friday, 13-Dec-2024 01:51:16 JST Mark Dominus

   in reply to

   My kids' schools never taught them short division, which seems to me a sad and odd omission.

   The idea is that instead of doing the big hairy thing on the left you do the compact speedy thing on the right. The left-side technique should only be used when the divisor is bigger than the multiplication tables you have memorized.

   The thing on the right is simple enough to do in your head, and particularly so if you only need the remainder and not the quotient. My kids were often mystified by my ability to divide in my head but it's just that I was taught a better algorithm than they were.

   I blogged about this a while back as part of a longer article about several methods of checking for divisibility by 7: https://blog.plover.com/math/divisibility-by-7.html