In year 3, we practised a lot with dienes and our place value knowledge to add and subtract before moving on to the column method.
The vocabulary we will use to talk about addition and subtraction might include:
- hundreds, tens and ones (the value of the digits in a 3-digit number)
- parts and the whole (part + part = whole; whole - part = part)
- commutative (in addition, it doesn't matter which way around the parts go, we get the same whole - for example, 3 + 4 = 7, 4 + 3 = 7. Subtraction is not commutative (7 - 4 does not equal the same answer as 4 - 7 because 4 - 7 would go past 0))
- regrouping (Sometimes, we need to regroup ones as tens and add them to our tens column, or do the same with our tens and hundreds. Sometimes, we might not have enough ones in our whole to subtract our part, so we regroup a ten to add 10 ones.)
These videos show children explaining and modelling the column method, so it should be understandable for your child to follow along too :)