New
New
Year 3

Add 2 and 3-digit numbers by redistributing

I can add 2 and 3-digit numbers by redistributing.

New
New
Year 3

Add 2 and 3-digit numbers by redistributing

I can add 2 and 3-digit numbers by redistributing.

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Lesson details

Key learning points

  1. If we subtract 1 from one addend, we must add one to the other added for the sum to remain the same
  2. When we redistribute, the total amount stays the same at all times
  3. Depending on the addends, we redistribute 1s or 10s

Common misconception

Pupils will sometimes remove or add ones or tens to one addend and forget to amend the other addend so that the calculation has been transformed but doesn't give the same sum as the original.

Encourage buddy checking of jottings as the children practise so that they can help each other to be reminded.

Keywords

  • Redistribute - Redistribution is a way of transforming a sum to make it easier to calculate mentally.

  • Inverse - The inverse is the opposite or reverse operation. For example, subtraction is the inverse operation of addition.

  • Efficient - Being efficient means finding a way to solve a problem quickly whilst also maintaining accuracy.

This strategy is shown with practical resources and jottings but the end goal is for the children be able to do it mentally so try to reduce such supports as quickly as possible.
Teacher tip

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).

Video

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6 Questions

Q1.
What is meant by the sum?
The answer to a multiplication question.
A calculation.
The difference between two numbers.
Correct answer: The total when numbers are added together.
Q2.
100 − 7 =
Correct Answer: 93, ninety three
Q3.
What is the complement to 100 of 92?
Correct Answer: 8, eight
Q4.
How far away is 97 from 100?
Correct Answer: 3, three
Q5.
Which of these base ten representations shows 68?
An image in a quiz
An image in a quiz
An image in a quiz
Correct Answer: An image in a quiz
An image in a quiz
Q6.
What number is being represented by base ten?
An image in a quiz
543
345
Correct answer: 354
453
435

6 Questions

Q1.
Match the expressions that are equal
Correct Answer:29 + 17,30 + 16

30 + 16

Correct Answer:20 + 35,19 + 36

19 + 36

Correct Answer:13 + 79,12 + 80

12 + 80

Q2.
Use redistribution to find the missing number. = 39 + 26
Correct Answer: 65, sixty five
Q3.
Use redistribution to find the missing number. = 530 + 190
Correct Answer: 720, seven hundred and twenty
Q4.
Use redistribution to find the missing number. = 150 + 397
Correct Answer: 547, five hundred and forty seven
Q5.
The base ten representation is showing a calculation being changed. The arrow shows some ones being redistributed. What is the transformed expression going to be?
An image in a quiz
Correct answer: 200 + 132
132 + 202
202 + 132
202 + 130
Q6.
156 ml of orange juice is mixed with 498 ml of pineapple juice. How many ml of juice is there altogether? ml
Correct Answer: 654, 654ml