Add two 3-digit numbers using adjusting strategies
I can adjust a number to make an addition easier.
Add two 3-digit numbers using adjusting strategies
I can adjust a number to make an addition easier.
These resources will be removed by end of Summer Term 2025.
Lesson details
Key learning points
- If you adjust an addend you adjust the sum by the inverse.
- If you add 1 to an addend you must subtract 1 from the sum.
- If you subtract 1 from an addend you must add 1 to the sum.
- A number line can represent the adjusting strategy.
Keywords
Adjust - When you adjust you make a small change to a number. This is done to make a calculation easier to solve mentally.
Inverse - The inverse is the opposite or reverse operation. For example, subtraction is the inverse operation of addition.
Efficient - Working efficiently means finding a way to solve a problem quickly whilst also maintaining accuracy.
Common misconception
Many pupils will want to use a written method/algorithm immediately such as column method. This lesson is to support mental addition strategies.
Encourage the children to forget about using written procedures because they are inefficient when the addends are suited to adjustment. As class teacher, use adjustment and race the children desperate to use columns to see who is fastest!
Licence
This content is © Oak National Academy Limited (2024), licensed on Open Government Licence version 3.0 except where otherwise stated. See Oak's terms & conditions (Collection 2).
Lesson video
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