When I was a wee sprog, I learned to do subtraction by borrowing and paying back. Like this:
It really hadn’t occured to me that there was another method until Bess was doing maths on the train on Friday evening (she made me write her out some sums to solve for fun!). She does her subtraction like this:
I thought it must be an age thing – Nancy had not seen this method either, but then I made Fenton do the same sum and he used the Bess method, so it has obviously been around for a while.
Okay, they are essentially the same thing, but it was really quite unsettling to see an unfamiliar technique on something I took for granted. I think I prefer the Bess method.
What method did you learn?
Many thanks to Nancy and Bess for their examples.