New
New
Add and subtract mentally without bridging a boundary
I can add and subtract mentally without bridging a boundary with one or more digits changing
Lesson 4 of 10
New
New
- Year 6
Add and subtract mentally without bridging a boundary
I can add and subtract mentally without bridging a boundary with one or more digits changing
Lesson details
Key learning points
- Known facts to 10 can be applied when adding and subtracting 100s, 1,000s, 10,000s and 100,000s
- When adding and subtracting mentally, the language of unitising supports us in addition to using known facts.
- An understanding of the structure of numbers and place value supports when we add and subtract mentally.
Keywords
Addend - An addend is a number added to another. They are also known as the parts.
Common misconception
Children may believe that only one digit will change when adding two numbers where one addend has only one non-zero digit.
This is usually correct but what would happen if the digit changed to a value of 10 or greater? Then we would need to regroup (another lesson).
The lesson should be as practical as possible, using place value counters and charts to support children to see the digits that change/s.
Teacher tip
Licence
This content is © Oak National Academy Limited (2025), 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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Prior knowledge starter quiz
6 Questions
Q1.Complete: is 3,000 more than 6,000
Complete: is 3,000 more than 6,000
Q2.1,306 + 400 =
1,306 + 400 =
Q3.Two plus three is equal to five so two thousand plus three thousand is equal to ___
Two plus three is equal to five so two thousand plus three thousand is equal to ___
5
50
500
50,000
Q4. is forty thousand less than ninety thousand. Give your answer as a numeral using digits.
is forty thousand less than ninety thousand. Give your answer as a numeral using digits.
Q5.6,709 − 3,000 = ___
6,709 − 3,000 = ___
6,409
6,739
9,709
Q6.Lucas thinks of a number. His number is 5,100 more than 13,215 What is his number?
Lucas thinks of a number. His number is 5,100 more than 13,215 What is his number?
Assessment exit quiz
6 Questions
Q1.3,901,481 + 3,000 = ___
3,901,481 + 3,000 = ___
3,091,781
3,931,481
3,903,481
Q2.Complete: 8,940,305 − 300,000 =
Complete: 8,940,305 − 300,000 =
Q3.Match the addends to their sum.
Match the addends to their sum.
Q4.7,154,302 + 500,000 − 400,000 =
7,154,302 + 500,000 − 400,000 =
Q5.Match the equations to their difference.
Match the equations to their difference.
Q6.Lucas thinks of a number. His number is 561,000 less than 3,994,314 What number is Lucas thinking of?
Lucas thinks of a number. His number is 561,000 less than 3,994,314 What number is Lucas thinking of?
