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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

icon-background-square
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

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Lesson details

Key learning points

  1. Known facts to 10 can be applied when adding and subtracting 100s, 1,000s, 10,000s and 100,000s
  2. When adding and subtracting mentally, the language of unitising supports us in addition to using known facts.
  3. 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.
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Lesson video

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6 Questions

Q1.
Complete: is 3,000 more than 6,000
Correct Answer: 9,000, 9000
Q2.
1,306 + 400 =
Correct Answer: 1,706, 1706
Q3.
Two plus three is equal to five so two thousand plus three thousand is equal to ___
5
50
500
Correct answer: 5,000
50,000
Q4.
is forty thousand less than ninety thousand. Give your answer as a numeral using digits.
Correct Answer: 50,000, 50000
Q5.
6,709 − 3,000 = ___
Correct answer: 3,709
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?
Correct Answer: 18,315, 18315

6 Questions

Q1.
3,901,481 + 3,000 = ___
3,091,781
3,931,481
3,903,481
Correct answer: 3,904,481
Q2.
Complete: 8,940,305 − 300,000 =
Correct Answer: 8,640,305, 8640305
Q3.
Match the addends to their sum.
Correct Answer:4,451,038 + 2,000,000 = ,6,451,038
tick

6,451,038

Correct Answer:4,451,038 + 200,000 =,4,651,038
tick

4,651,038

Correct Answer:4,451,038 + 20,000 =,4,471,038
tick

4,471,038

Correct Answer:4,451,038 + 2,000 =,4,453,038
tick

4,453,038

Correct Answer:4,451,038 + 200 =,4,451,238
tick

4,451,238

Q4.
7,154,302 + 500,000 − 400,000 =
Correct Answer: 7,254,302, 7254302
Q5.
Match the equations to their difference.
Correct Answer:8,296,792 − 31,000 =,8,265,792
tick

8,265,792

Correct Answer:8,296,792 − 31,500 =,8,265,292
tick

8,265,292

Correct Answer:8,296,792 − 31,520 =,8,265,272
tick

8,265,272

Correct Answer:8,296,792 − 31,524 =,8,265,268
tick

8,265,268

Q6.
Lucas thinks of a number. His number is 561,000 less than 3,994,314 What number is Lucas thinking of?
Correct Answer: 3,433,314, 3433314