Resources
Adding three 3-digit numbers
The method that is used in the lesson is ‘compact addition’. Any ‘tens’, ‘hundreds’ or ‘hundreds’ that are carried forward are shown in red and are placed in the correct column under the numbers being added. If I was teaching this I would place these carried amounts under the second line – see below (coloured red). The line for me separates them from the original three numbers. However, it doesn’t matter which way you do – both methods basically the same but slightly different layouts and achieve the same answer!
If I was teaching this in class, I would usually put which place value each column represented to help children understand the value of each digit (in blue):
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Th |
H |
T |
O |
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4 |
2 |
6 |
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2 |
5 |
7 |
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5 |
8 |
2 |
|
1 |
2 |
6 |
5 |
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1 |
1 |
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These websites are worth a look:
Column Addition (Maths is Fun)
What is column addition? (BBC Bitesize)
Decimal Notation (BBC Bitesize)
Commutative, Associative and Distributive Laws (Maths is Fun)
Maths KS1 / KS2: How to use mental methods to multiply (BBC Teacher)