Puffin she has no trouble at all with things like 10-5, 50-5, 20-10, 50-20, 20+50+5, etc anything I could demonstrate with our coinage I am very confident that even if she was slow she would be accurate (though its hard to say if having the coins in hand would slow her down or speed her up, compared to being asked verbally I could time it, I think she'd be faster verbally). Her problem is NOT with the concept of addition or subtraction.
I am particulalry sure about the coins given her approach to 50-20 would be "thats 5-2, so 30". I think the problem is fundamentally that she's no doing it in her head using memory or patterns like that when regrouping is required, because regrouping requires that you know subtraction for 11-20 or are fast and reliable at working it out. And she's got neither. Like zen scanner said I wouldn't have thought you need to know above 10, but working with her ive realise I do just KNOW the bond between 5, 7 and 12, or 8,8 and 16, etc, I also use tricks around 1s, 5s 9s and 10s. She's not got any of that and I'm not sure why (or why it's hard).
I'm hoping zen scanner has hit on it with the last post. I need to read that link on a real computer.
Maybe I should try teaching times tables and all the patterns and tricks for learning them, Imaybe that's what she needs to get this.
