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How do they teach subtraction in France?!

(5 Posts)
Raptorrrethy Mon 17-Mar-14 16:52:36

DD is in CE2 and I am baffled by the method she is being taught to subtract…e.g., 1412-58 involves writing '1' on both the top set of numbers AND the bottom. I was taught to 'borrow' from the number on the left, if that makes sense, but I never change anything with the smaller number (in this case the 58).
If she was getting the answers right I would probably just leave her to it, but she is not…clearly she has not understood it in class or there is one crucial thing she is doing wrong.

I am going to ask la maitresse to explain it to DD again but in the meantime, can anyone explain it to me?? confused

ilovepowerhoop Mon 17-Mar-14 21:41:44

I think I did it the way your dd is being taught ie you would add 10 to the 2 to make it 12 and then add a 1 at the 5 to make it 6

1412
- 58

would become

14¹1¹2
- ¹ ¹5 8
----
13 5 4

so the 2 becomes 12 and taking 8 away from it makes 4. You cant take 6 away from 1 so again you add 10 to the 1 and put a 1 under the 4. 11 take away 6 is 5. 4 take away the 1 is 3 and 1 take away 0 is 1.

ilovepowerhoop Mon 17-Mar-14 21:45:16

dont know if that makes much sense but its the way I was taught. DH was taught your way which is also the way dd is being taught so I find your method tricky.

ilovepowerhoop Mon 17-Mar-14 21:47:01

www.mathsteacher.com.au/year7/ch01_whole/03_sub/sub.htm - this seems to explain it

Raptorrrethy Mon 17-Mar-14 21:55:04

Thank you - I'll check out the link. Funny how we feel most secure with what we were taught to begin with!

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